diff --git a/nbgrader/docs/source/plugins/late-plugin.rst b/nbgrader/docs/source/plugins/late-plugin.rst
index d28c33ef..8bed2d17 100644
--- a/nbgrader/docs/source/plugins/late-plugin.rst
+++ b/nbgrader/docs/source/plugins/late-plugin.rst
@@ -7,7 +7,7 @@ nbgrader will still compute how late each submission is.
 
 For this to work, you must include a duedate for the assignment and then a
 ``timestamp.txt`` file in the folder for each submission with a single line
-containing a timestamp (e.g. ``2015-02-02 14:58:23.948203 PST``).
+containing a timestamp (e.g. ``2015-02-02 14:58:23.948203 America/Los_Angeles``).
 Then, when you run ``nbgrader autograde``, nbgrader will record these
 timestamps into the database, compute how late each submission is and assign a
 late penalty (if specified). Also see the :doc:`faq </user_guide/faq>`.
diff --git a/nbgrader/docs/source/user_guide/autograded/bitdiddle/ps1/timestamp.txt b/nbgrader/docs/source/user_guide/autograded/bitdiddle/ps1/timestamp.txt
index dddadbe7..bf5f1f73 100644
--- a/nbgrader/docs/source/user_guide/autograded/bitdiddle/ps1/timestamp.txt
+++ b/nbgrader/docs/source/user_guide/autograded/bitdiddle/ps1/timestamp.txt
@@ -1,1 +1,1 @@
-2015-02-02 14:58:23.948203 PST
+2015-02-02 14:58:23.948203 America/Los_Angeles
diff --git a/nbgrader/docs/source/user_guide/autograded/hacker/ps1/timestamp.txt b/nbgrader/docs/source/user_guide/autograded/hacker/ps1/timestamp.txt
index 9ddce64e..c74791df 100644
--- a/nbgrader/docs/source/user_guide/autograded/hacker/ps1/timestamp.txt
+++ b/nbgrader/docs/source/user_guide/autograded/hacker/ps1/timestamp.txt
@@ -1,1 +1,1 @@
-2015-02-01 09:28:58.749302 PST
+2015-02-01 09:28:58.749302 America/Los_Angeles
diff --git a/nbgrader/docs/source/user_guide/faq.rst b/nbgrader/docs/source/user_guide/faq.rst
index 719a5900..5921b46a 100644
--- a/nbgrader/docs/source/user_guide/faq.rst
+++ b/nbgrader/docs/source/user_guide/faq.rst
@@ -54,7 +54,7 @@ behavior see :doc:`adding customization plugins </plugins/index>`.
 
 For this to work, you must include a duedate for the assignment and then a
 ``timestamp.txt`` file in the folder for each submission with a single line
-containing a timestamp (e.g. ``2015-02-02 14:58:23.948203 PST``). Then, when
+containing a timestamp (e.g. ``2015-02-02 14:58:23.948203 America/Los_Angeles``). Then, when
 you run ``nbgrader autograde``, nbgrader will record these timestamps into the
 database. You can access the timestamps through the API, like so:
 
diff --git a/nbgrader/docs/source/user_guide/feedback/bitdiddle/ps1/timestamp.txt b/nbgrader/docs/source/user_guide/feedback/bitdiddle/ps1/timestamp.txt
index dddadbe7..bf5f1f73 100644
--- a/nbgrader/docs/source/user_guide/feedback/bitdiddle/ps1/timestamp.txt
+++ b/nbgrader/docs/source/user_guide/feedback/bitdiddle/ps1/timestamp.txt
@@ -1,1 +1,1 @@
-2015-02-02 14:58:23.948203 PST
+2015-02-02 14:58:23.948203 America/Los_Angeles
diff --git a/nbgrader/docs/source/user_guide/feedback/hacker/ps1/timestamp.txt b/nbgrader/docs/source/user_guide/feedback/hacker/ps1/timestamp.txt
index 9ddce64e..c74791df 100644
--- a/nbgrader/docs/source/user_guide/feedback/hacker/ps1/timestamp.txt
+++ b/nbgrader/docs/source/user_guide/feedback/hacker/ps1/timestamp.txt
@@ -1,1 +1,1 @@
-2015-02-01 09:28:58.749302 PST
+2015-02-01 09:28:58.749302 America/Los_Angeles
diff --git a/nbgrader/docs/source/user_guide/submitted/bitdiddle/ps1/timestamp.txt b/nbgrader/docs/source/user_guide/submitted/bitdiddle/ps1/timestamp.txt
index dddadbe7..bf5f1f73 100644
--- a/nbgrader/docs/source/user_guide/submitted/bitdiddle/ps1/timestamp.txt
+++ b/nbgrader/docs/source/user_guide/submitted/bitdiddle/ps1/timestamp.txt
@@ -1,1 +1,1 @@
-2015-02-02 14:58:23.948203 PST
+2015-02-02 14:58:23.948203 America/Los_Angeles
diff --git a/nbgrader/docs/source/user_guide/submitted/hacker/ps1/timestamp.txt b/nbgrader/docs/source/user_guide/submitted/hacker/ps1/timestamp.txt
index 9ddce64e..c74791df 100644
--- a/nbgrader/docs/source/user_guide/submitted/hacker/ps1/timestamp.txt
+++ b/nbgrader/docs/source/user_guide/submitted/hacker/ps1/timestamp.txt
@@ -1,1 +1,1 @@
-2015-02-01 09:28:58.749302 PST
+2015-02-01 09:28:58.749302 America/Los_Angeles
diff --git a/nbgrader/utils.py b/nbgrader/utils.py
index 55f440ab..f7f2975f 100644
--- a/nbgrader/utils.py
+++ b/nbgrader/utils.py
@@ -115,7 +115,17 @@ def parse_utc(ts):
     if ts is None:
         return None
     if isinstance(ts, six.string_types):
-        ts = dateutil.parser.parse(ts)
+        parts = ts.split(" ")
+        if len(parts) == 3:
+            ts = " ".join(parts[:2] + ["TZ"])
+            tz = parts[2]
+            try:
+                tz = int(tz)
+            except ValueError:
+                tz = dateutil.tz.gettz(tz)
+            ts = dateutil.parser.parse(ts, tzinfos=dict(TZ=tz))
+        else:
+            ts = dateutil.parser.parse(ts)
     if ts.tzinfo is not None:
         ts = (ts - ts.utcoffset()).replace(tzinfo=None)
     return ts

Fix warning with timezones
Somewhere in the tests the following warning is being raised:

```
  /home/jhamrick/miniconda3/lib/python3.6/site-packages/dateutil/parser/_parser.py:1165: UnknownTimezoneWarning: tzname PST identified but not understood.  Pass `tzinfos` argument in order to correctly return a timezone-aware datetime.  In a future version, this raise an exception.
    category=UnknownTimezoneWarning)
```

This should be addressed before it turns into an exception.
diff --git a/nbgrader/tests/api/test_gradebook.py b/nbgrader/tests/api/test_gradebook.py
index bb6b072e..6367ea92 100644
--- a/nbgrader/tests/api/test_gradebook.py
+++ b/nbgrader/tests/api/test_gradebook.py
@@ -174,9 +174,9 @@ def test_update_or_create_assignment(gradebook):
     assert a1.duedate is None
 
     # now test finding/updating it
-    a2 = gradebook.update_or_create_assignment('foo', duedate="2015-02-02 14:58:23.948203 PST")
+    a2 = gradebook.update_or_create_assignment('foo', duedate="2015-02-02 14:58:23.948203 America/Los_Angeles")
     assert a1 == a2
-    assert a2.duedate == utils.parse_utc("2015-02-02 14:58:23.948203 PST")
+    assert a2.duedate == utils.parse_utc("2015-02-02 14:58:23.948203 America/Los_Angeles")
 
 
 #### Test notebooks
@@ -532,9 +532,9 @@ def test_update_or_create_submission(assignment):
     s1 = assignment.update_or_create_submission('foo', 'hacker123')
     assert s1.timestamp is None
 
-    s2 = assignment.update_or_create_submission('foo', 'hacker123', timestamp="2015-02-02 14:58:23.948203 PST")
+    s2 = assignment.update_or_create_submission('foo', 'hacker123', timestamp="2015-02-02 14:58:23.948203 America/Los_Angeles")
     assert s1 == s2
-    assert s2.timestamp == utils.parse_utc("2015-02-02 14:58:23.948203 PST")
+    assert s2.timestamp == utils.parse_utc("2015-02-02 14:58:23.948203 America/Los_Angeles")
 
 
 def test_find_submission_notebook(assignment):
diff --git a/nbgrader/tests/apps/test_nbgrader_autograde.py b/nbgrader/tests/apps/test_nbgrader_autograde.py
index 02cfbcbd..53bab0bc 100644
--- a/nbgrader/tests/apps/test_nbgrader_autograde.py
+++ b/nbgrader/tests/apps/test_nbgrader_autograde.py
@@ -26,7 +26,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_missing_student(self, db, course_dir):
         """Is an error thrown when the student is missing?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-changed.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -41,7 +41,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_missing_assignment(self, db, course_dir):
         """Is an error thrown when the assignment is missing?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-changed.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -53,7 +53,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_grade(self, db, course_dir):
         """Can files be graded?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -95,17 +95,17 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_grade_timestamp(self, db, course_dir):
         """Is a timestamp correctly read in?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
         run_nbgrader(["assign", "ps1", "--db", db])
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
 
         self._copy_file(join("files", "submitted-changed.ipynb"), join(course_dir, "submitted", "bar", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-01 14:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-01 14:58:23.948203 America/Los_Angeles")
 
         run_nbgrader(["autograde", "ps1", "--db", db])
 
@@ -127,7 +127,7 @@ class TestNbGraderAutograde(BaseTestApp):
         """Issue #580 - Does the autograder handle empty or invalid timestamp
         strings"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -152,7 +152,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_late_submission_penalty_none(self, db, course_dir):
         """Does 'none' method do nothing?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -160,11 +160,11 @@ class TestNbGraderAutograde(BaseTestApp):
 
         # not late
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 14:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 14:58:23.948203 America/Los_Angeles")
 
         # 1h late
         self._copy_file(join("files", "submitted-changed.ipynb"), join(course_dir, "submitted", "bar", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
 
         run_nbgrader(["autograde", "ps1", "--db", db])
 
@@ -191,7 +191,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_late_submission_penalty_zero(self, db, course_dir):
         """Does 'zero' method assign notebook.score as penalty if late?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]\n""")
             fh.write("""c.LateSubmissionPlugin.penalty_method = 'zero'""")
 
@@ -200,11 +200,11 @@ class TestNbGraderAutograde(BaseTestApp):
 
         # not late
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 14:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 14:58:23.948203 America/Los_Angeles")
 
         # 1h late
         self._copy_file(join("files", "submitted-changed.ipynb"), join(course_dir, "submitted", "bar", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
 
         run_nbgrader(["autograde", "ps1", "--db", db])
 
@@ -229,7 +229,7 @@ class TestNbGraderAutograde(BaseTestApp):
             assert nb.late_submission_penalty == nb.score
 
         # Issue 723 - check penalty is reset if timestamp changed
-        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-02 14:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-02 14:58:23.948203 America/Los_Angeles")
         run_nbgrader(["autograde", "--force", "ps1", "--db", db])
 
         with Gradebook(db) as gb:
@@ -258,7 +258,7 @@ class TestNbGraderAutograde(BaseTestApp):
             fh.write(plugin)
 
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]\n""")
             fh.write("""c.AssignLatePenalties.plugin_class = 'late_plugin.Blarg'""")
 
@@ -267,11 +267,11 @@ class TestNbGraderAutograde(BaseTestApp):
 
         # 4h late
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 18:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 18:58:23.948203 America/Los_Angeles")
 
         # 1h late
         self._copy_file(join("files", "submitted-changed.ipynb"), join(course_dir, "submitted", "bar", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "bar", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
 
         run_nbgrader(["autograde", "ps1", "--db", db])
 
@@ -298,7 +298,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_force(self, db, course_dir):
         """Ensure the force option works properly"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -338,7 +338,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_force_f(self, db, course_dir):
         """Ensure the force option works properly"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -378,7 +378,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_filter_notebook(self, db, course_dir):
         """Does autograding filter by notebook properly?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -428,7 +428,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_grade_overwrite_files(self, db, course_dir):
         """Are dependent files properly linked and overwritten?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]\n""")
             fh.write("""c.Autograde.exclude_overwriting = {"ps1": ["helper.py"]}\n""")
 
@@ -438,7 +438,7 @@ class TestNbGraderAutograde(BaseTestApp):
         run_nbgrader(["assign", "ps1", "--db", db])
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
         self._make_file(join(course_dir, "submitted", "foo", "ps1", "data.csv"), "some,other,data\n")
         self._make_file(join(course_dir, "submitted", "foo", "ps1", "helper.py"), "print('this is different!')\n")
         run_nbgrader(["autograde", "ps1", "--db", db])
@@ -450,7 +450,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
         with open(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"), "r") as fh:
             contents = fh.read()
-        assert contents == "2015-02-02 15:58:23.948203 PST"
+        assert contents == "2015-02-02 15:58:23.948203 America/Los_Angeles"
 
         with open(join(course_dir, "autograded", "foo", "ps1", "data.csv"), "r") as fh:
             contents = fh.read()
@@ -463,7 +463,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_grade_overwrite_files_subdirs(self, db, course_dir):
         """Are dependent files properly linked and overwritten?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]\n""")
             fh.write("""c.Autograde.exclude_overwriting = {{"ps1": ["{}"]}}\n""".format(os.path.join("subdir", "helper.py")))
 
@@ -473,7 +473,7 @@ class TestNbGraderAutograde(BaseTestApp):
         run_nbgrader(["assign", "ps1", "--db", db])
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
         self._make_file(join(course_dir, "submitted", "foo", "ps1", "subdir", "data.csv"), "some,other,data\n")
         self._make_file(join(course_dir, "submitted", "foo", "ps1", "subdir", "helper.py"), "print('this is different!')\n")
         run_nbgrader(["autograde", "ps1", "--db", db])
@@ -485,7 +485,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
         with open(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"), "r") as fh:
             contents = fh.read()
-        assert contents == "2015-02-02 15:58:23.948203 PST"
+        assert contents == "2015-02-02 15:58:23.948203 America/Los_Angeles"
 
         with open(join(course_dir, "autograded", "foo", "ps1", "subdir", "data.csv"), "r") as fh:
             contents = fh.read()
@@ -497,7 +497,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_side_effects(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "side-effects.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -511,7 +511,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_skip_extra_notebooks(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -527,7 +527,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_permissions(self, course_dir):
         """Are permissions properly set?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._empty_notebook(join(course_dir, "source", "ps1", "foo.ipynb"))
@@ -546,7 +546,7 @@ class TestNbGraderAutograde(BaseTestApp):
     def test_custom_permissions(self, course_dir):
         """Are custom permissions properly set?"""
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._empty_notebook(join(course_dir, "source", "ps1", "foo.ipynb"))
@@ -569,7 +569,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_force_single_notebook(self, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -597,33 +597,33 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_update_newer(self, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
         run_nbgrader(["assign", "ps1"])
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
         run_nbgrader(["autograde", "ps1"])
 
         assert os.path.isfile(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
         assert os.path.isfile(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"))
-        assert self._file_contents(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt")) == "2015-02-02 15:58:23.948203 PST"
+        assert self._file_contents(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt")) == "2015-02-02 15:58:23.948203 America/Los_Angeles"
         p = self._file_contents(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
 
         self._empty_notebook(join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 16:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 16:58:23.948203 America/Los_Angeles")
         run_nbgrader(["autograde", "ps1"])
 
         assert os.path.isfile(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
         assert os.path.isfile(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"))
-        assert self._file_contents(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt")) == "2015-02-02 16:58:23.948203 PST"
+        assert self._file_contents(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt")) == "2015-02-02 16:58:23.948203 America/Los_Angeles"
         assert p != self._file_contents(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
 
     def test_update_newer_single_notebook(self, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -632,32 +632,32 @@ class TestNbGraderAutograde(BaseTestApp):
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p2.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
         run_nbgrader(["autograde", "ps1"])
 
         assert os.path.exists(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
         assert os.path.exists(join(course_dir, "autograded", "foo", "ps1", "p2.ipynb"))
         assert os.path.isfile(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"))
-        assert self._file_contents(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt")) == "2015-02-02 15:58:23.948203 PST"
+        assert self._file_contents(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt")) == "2015-02-02 15:58:23.948203 America/Los_Angeles"
         p1 = self._file_contents(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
         p2 = self._file_contents(join(course_dir, "autograded", "foo", "ps1", "p2.ipynb"))
         assert p1 == p2
 
         self._empty_notebook(join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
         self._empty_notebook(join(course_dir, "submitted", "foo", "ps1", "p2.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 16:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 16:58:23.948203 America/Los_Angeles")
         run_nbgrader(["autograde", "ps1", "--notebook", "p1"])
 
         assert os.path.exists(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
         assert os.path.exists(join(course_dir, "autograded", "foo", "ps1", "p2.ipynb"))
         assert os.path.isfile(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"))
-        assert self._file_contents(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt")) == "2015-02-02 16:58:23.948203 PST"
+        assert self._file_contents(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt")) == "2015-02-02 16:58:23.948203 America/Los_Angeles"
         assert p1 != self._file_contents(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
         assert p2 == self._file_contents(join(course_dir, "autograded", "foo", "ps1", "p2.ipynb"))
 
     def test_hidden_tests_single_notebook(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]\n""")
             fh.write("""c.ClearSolutions.code_stub=dict(python="# YOUR CODE HERE")""")
 
@@ -711,7 +711,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_handle_failure(self, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._empty_notebook(join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -729,7 +729,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_handle_failure_single_notebook(self, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._empty_notebook(join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -746,7 +746,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_missing_source_kernelspec(self, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]\n""")
             fh.write("""c.ClearSolutions.code_stub = {'python': '## Answer', 'blah': '## Answer'}""")
 
@@ -764,7 +764,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_incorrect_source_kernelspec(self, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]\n""")
             fh.write("""c.ClearSolutions.code_stub = {'python': '## Answer', 'blah': '## Answer'}""")
 
@@ -777,7 +777,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_incorrect_submitted_kernelspec(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._empty_notebook(join(course_dir, "source", "ps1", "p1.ipynb"), kernel="python")
@@ -790,7 +790,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_no_execute(self, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo")]""")
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -845,7 +845,7 @@ class TestNbGraderAutograde(BaseTestApp):
             students.append(dict(id=student_fmt.format(i)))
 
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = {}""".format(json.dumps(students)))
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -858,7 +858,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_infinite_loop(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo")]\n""")
             fh.write("""c.ExecutePreprocessor.timeout = 1""")
 
@@ -874,7 +874,7 @@ class TestNbGraderAutograde(BaseTestApp):
         pytest.skip("this test takes too long to run and consumes a LOT of memory")
 
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo")]\n""")
 
         self._copy_file(join("files", "infinite-loop-with-output.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -887,7 +887,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_missing_files(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._empty_notebook(join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -903,7 +903,7 @@ class TestNbGraderAutograde(BaseTestApp):
 
     def test_grade_missing_notebook(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
diff --git a/nbgrader/tests/apps/test_nbgrader_export.py b/nbgrader/tests/apps/test_nbgrader_export.py
index 79194639..9f56ff92 100644
--- a/nbgrader/tests/apps/test_nbgrader_export.py
+++ b/nbgrader/tests/apps/test_nbgrader_export.py
@@ -15,8 +15,8 @@ class TestNbGraderExport(BaseTestApp):
     def test_export(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
             fh.write("""c.CourseDirectory.db_assignments = [
-                dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST'),
-                dict(name='ps2', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+                dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles'),
+                dict(name='ps2', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "submitted-unchanged.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
diff --git a/nbgrader/tests/apps/test_nbgrader_feedback.py b/nbgrader/tests/apps/test_nbgrader_feedback.py
index 20fb7a75..c8284862 100644
--- a/nbgrader/tests/apps/test_nbgrader_feedback.py
+++ b/nbgrader/tests/apps/test_nbgrader_feedback.py
@@ -227,22 +227,22 @@ class TestNbGraderFeedback(BaseTestApp):
         run_nbgrader(["assign", "ps1"])
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
         run_nbgrader(["autograde", "ps1"])
         run_nbgrader(["feedback", "ps1"])
 
         assert isfile(join(course_dir, "feedback", "foo", "ps1", "p1.html"))
         assert isfile(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt"))
-        assert self._file_contents(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt")) == "2015-02-02 15:58:23.948203 PST"
+        assert self._file_contents(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt")) == "2015-02-02 15:58:23.948203 America/Los_Angeles"
         p = self._file_contents(join(course_dir, "feedback", "foo", "ps1", "p1.html"))
 
         self._empty_notebook(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
-        self._make_file(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"), "2015-02-02 16:58:23.948203 PST")
+        self._make_file(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"), "2015-02-02 16:58:23.948203 America/Los_Angeles")
         run_nbgrader(["feedback", "ps1"])
 
         assert isfile(join(course_dir, "feedback", "foo", "ps1", "p1.html"))
         assert isfile(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt"))
-        assert self._file_contents(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt")) == "2015-02-02 16:58:23.948203 PST"
+        assert self._file_contents(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt")) == "2015-02-02 16:58:23.948203 America/Los_Angeles"
         assert p != self._file_contents(join(course_dir, "feedback", "foo", "ps1", "p1.html"))
 
     def test_update_newer_single_notebook(self, course_dir):
@@ -255,25 +255,25 @@ class TestNbGraderFeedback(BaseTestApp):
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p1.ipynb"))
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "submitted", "foo", "ps1", "p2.ipynb"))
-        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 PST")
+        self._make_file(join(course_dir, "submitted", "foo", "ps1", "timestamp.txt"), "2015-02-02 15:58:23.948203 America/Los_Angeles")
         run_nbgrader(["autograde", "ps1"])
         run_nbgrader(["feedback", "ps1"])
 
         assert exists(join(course_dir, "feedback", "foo", "ps1", "p1.html"))
         assert exists(join(course_dir, "feedback", "foo", "ps1", "p2.html"))
         assert isfile(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt"))
-        assert self._file_contents(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt")) == "2015-02-02 15:58:23.948203 PST"
+        assert self._file_contents(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt")) == "2015-02-02 15:58:23.948203 America/Los_Angeles"
         p1 = self._file_contents(join(course_dir, "feedback", "foo", "ps1", "p1.html"))
         p2 = self._file_contents(join(course_dir, "feedback", "foo", "ps1", "p2.html"))
 
         self._empty_notebook(join(course_dir, "autograded", "foo", "ps1", "p1.ipynb"))
         self._empty_notebook(join(course_dir, "autograded", "foo", "ps1", "p2.ipynb"))
-        self._make_file(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"), "2015-02-02 16:58:23.948203 PST")
+        self._make_file(join(course_dir, "autograded", "foo", "ps1", "timestamp.txt"), "2015-02-02 16:58:23.948203 America/Los_Angeles")
         run_nbgrader(["feedback", "ps1", "--notebook", "p1"])
 
         assert exists(join(course_dir, "feedback", "foo", "ps1", "p1.html"))
         assert exists(join(course_dir, "feedback", "foo", "ps1", "p2.html"))
         assert isfile(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt"))
-        assert self._file_contents(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt")) == "2015-02-02 16:58:23.948203 PST"
+        assert self._file_contents(join(course_dir, "feedback", "foo", "ps1", "timestamp.txt")) == "2015-02-02 16:58:23.948203 America/Los_Angeles"
         assert p1 != self._file_contents(join(course_dir, "feedback", "foo", "ps1", "p1.html"))
         assert p2 == self._file_contents(join(course_dir, "feedback", "foo", "ps1", "p2.html"))
diff --git a/nbgrader/tests/apps/test_nbgrader_update.py b/nbgrader/tests/apps/test_nbgrader_update.py
index 0432556d..a58dd511 100644
--- a/nbgrader/tests/apps/test_nbgrader_update.py
+++ b/nbgrader/tests/apps/test_nbgrader_update.py
@@ -48,7 +48,7 @@ class TestNbGraderUpdate(BaseTestApp):
 
     def test_update_assign(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "test-v0.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -62,7 +62,7 @@ class TestNbGraderUpdate(BaseTestApp):
 
     def test_update_autograde(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "test.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))
@@ -80,7 +80,7 @@ class TestNbGraderUpdate(BaseTestApp):
 
     def test_update_autograde_old_assign(self, db, course_dir):
         with open("nbgrader_config.py", "a") as fh:
-            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 PST')]\n""")
+            fh.write("""c.CourseDirectory.db_assignments = [dict(name='ps1', duedate='2015-02-02 14:58:23.948203 America/Los_Angeles')]\n""")
             fh.write("""c.CourseDirectory.db_students = [dict(id="foo"), dict(id="bar")]""")
 
         self._copy_file(join("files", "test-v0.ipynb"), join(course_dir, "source", "ps1", "p1.ipynb"))

pip install -e .[dev]
parse_log_pytest
requirements.txt
pytest pytest-cov pytest-rerunfailures coverage selenium invoke sphinx codecov cov-core pytest
apt-get update apt-get install -y gcc
3.6
dev-requirements.txt dev-requirements-windows.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
alabaster==0.7.13
alembic==1.7.7
anyio==3.6.2
argon2-cffi==21.3.0
argon2-cffi-bindings==21.2.0
async-generator==1.10
attrs==22.2.0
Babel==2.11.0
backcall==0.2.0
bleach==4.1.0
certifi==2021.5.30
cffi==1.15.1
charset-normalizer==2.0.12
codecov==2.1.13
comm==0.1.4
contextvars==2.4
cov-core==1.15.0
coverage==6.2
dataclasses==0.8
decorator==5.1.1
defusedxml==0.7.1
docutils==0.18.1
entrypoints==0.4
fuzzywuzzy==0.18.0
greenlet==2.0.2
idna==3.10
imagesize==1.4.1
immutables==0.19
importlib-metadata==4.8.3
importlib-resources==5.4.0
iniconfig==1.1.1
invoke==2.2.0
ipykernel==5.5.6
ipython==7.16.3
ipython-genutils==0.2.0
ipywidgets==7.8.5
jedi==0.17.2
Jinja2==3.0.3
json5==0.9.16
jsonschema==3.2.0
jupyter==1.1.1
jupyter-client==7.1.2
jupyter-console==6.4.3
jupyter-core==4.9.2
jupyter-server==1.13.1
jupyterlab==3.2.9
jupyterlab-pygments==0.1.2
jupyterlab-server==2.10.3
jupyterlab_widgets==1.1.11
Mako==1.1.6
MarkupSafe==2.0.1
mistune==0.8.4
nbclassic==0.3.5
nbclient==0.5.9
nbconvert==6.0.7
nbformat==5.1.3
-e git+https://github.com/jupyter/nbgrader.git@25878a1dcdd0e7aa1bb43794924f2e5ee9f82768#egg=nbgrader
nbval==0.10.0
nest-asyncio==1.6.0
notebook==6.4.10
packaging==21.3
pandocfilters==1.5.1
parso==0.7.1
pexpect==4.9.0
pickleshare==0.7.5
pluggy==1.0.0
prometheus-client==0.17.1
prompt-toolkit==3.0.36
ptyprocess==0.7.0
py==1.11.0
pycparser==2.21
pyenchant==3.2.2
Pygments==2.14.0
pyparsing==3.1.4
pyrsistent==0.18.0
pytest==7.0.1
pytest-cov==4.0.0
pytest-rerunfailures==10.3
python-dateutil==2.9.0.post0
pytz==2025.2
pyzmq==25.1.2
requests==2.27.1
selenium==3.141.0
Send2Trash==1.8.3
six==1.17.0
sniffio==1.2.0
snowballstemmer==2.2.0
Sphinx==5.3.0
sphinx-rtd-theme==2.0.0
sphinxcontrib-applehelp==1.0.2
sphinxcontrib-devhelp==1.0.2
sphinxcontrib-htmlhelp==2.0.0
sphinxcontrib-jquery==4.1
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==1.0.3
sphinxcontrib-serializinghtml==1.1.5
sphinxcontrib-spelling==7.7.0
SQLAlchemy==1.4.54
terminado==0.12.1
testpath==0.6.0
tomli==1.2.3
tornado==6.1
traitlets==4.3.3
typing_extensions==4.1.1
urllib3==1.26.20
wcwidth==0.2.13
webencodings==0.5.1
websocket-client==1.3.1
widgetsnbextension==3.6.10
zipp==3.6.0

name: nbgrader
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - pip=21.2.2=py36h06a4308_0
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - alabaster==0.7.13
      - alembic==1.7.7
      - anyio==3.6.2
      - argon2-cffi==21.3.0
      - argon2-cffi-bindings==21.2.0
      - async-generator==1.10
      - attrs==22.2.0
      - babel==2.11.0
      - backcall==0.2.0
      - bleach==4.1.0
      - cffi==1.15.1
      - charset-normalizer==2.0.12
      - codecov==2.1.13
      - comm==0.1.4
      - contextvars==2.4
      - cov-core==1.15.0
      - coverage==6.2
      - dataclasses==0.8
      - decorator==5.1.1
      - defusedxml==0.7.1
      - docutils==0.18.1
      - entrypoints==0.4
      - fuzzywuzzy==0.18.0
      - greenlet==2.0.2
      - idna==3.10
      - imagesize==1.4.1
      - immutables==0.19
      - importlib-metadata==4.8.3
      - importlib-resources==5.4.0
      - iniconfig==1.1.1
      - invoke==2.2.0
      - ipykernel==5.5.6
      - ipython==7.16.3
      - ipython-genutils==0.2.0
      - ipywidgets==7.8.5
      - jedi==0.17.2
      - jinja2==3.0.3
      - json5==0.9.16
      - jsonschema==3.2.0
      - jupyter==1.1.1
      - jupyter-client==7.1.2
      - jupyter-console==6.4.3
      - jupyter-core==4.9.2
      - jupyter-server==1.13.1
      - jupyterlab==3.2.9
      - jupyterlab-pygments==0.1.2
      - jupyterlab-server==2.10.3
      - jupyterlab-widgets==1.1.11
      - mako==1.1.6
      - markupsafe==2.0.1
      - mistune==0.8.4
      - nbclassic==0.3.5
      - nbclient==0.5.9
      - nbconvert==6.0.7
      - nbformat==5.1.3
      - nbval==0.10.0
      - nest-asyncio==1.6.0
      - notebook==6.4.10
      - packaging==21.3
      - pandocfilters==1.5.1
      - parso==0.7.1
      - pexpect==4.9.0
      - pickleshare==0.7.5
      - pluggy==1.0.0
      - prometheus-client==0.17.1
      - prompt-toolkit==3.0.36
      - ptyprocess==0.7.0
      - py==1.11.0
      - pycparser==2.21
      - pyenchant==3.2.2
      - pygments==2.14.0
      - pyparsing==3.1.4
      - pyrsistent==0.18.0
      - pytest==7.0.1
      - pytest-cov==4.0.0
      - pytest-rerunfailures==10.3
      - python-dateutil==2.9.0.post0
      - pytz==2025.2
      - pyzmq==25.1.2
      - requests==2.27.1
      - selenium==3.141.0
      - send2trash==1.8.3
      - six==1.17.0
      - sniffio==1.2.0
      - snowballstemmer==2.2.0
      - sphinx==5.3.0
      - sphinx-rtd-theme==2.0.0
      - sphinxcontrib-applehelp==1.0.2
      - sphinxcontrib-devhelp==1.0.2
      - sphinxcontrib-htmlhelp==2.0.0
      - sphinxcontrib-jquery==4.1
      - sphinxcontrib-jsmath==1.0.1
      - sphinxcontrib-qthelp==1.0.3
      - sphinxcontrib-serializinghtml==1.1.5
      - sphinxcontrib-spelling==7.7.0
      - sqlalchemy==1.4.54
      - terminado==0.12.1
      - testpath==0.6.0
      - tomli==1.2.3
      - tornado==6.1
      - traitlets==4.3.3
      - typing-extensions==4.1.1
      - urllib3==1.26.20
      - wcwidth==0.2.13
      - webencodings==0.5.1
      - websocket-client==1.3.1
      - widgetsnbextension==3.6.10
      - zipp==3.6.0
prefix: /opt/conda/envs/nbgrader

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