diff --git a/conans/__init__.py b/conans/__init__.py
index 97c78e433..2333a851a 100644
--- a/conans/__init__.py
+++ b/conans/__init__.py
@@ -16,5 +16,5 @@ COMPLEX_SEARCH_CAPABILITY = "complex_search"
 SERVER_CAPABILITIES = [COMPLEX_SEARCH_CAPABILITY, ]
 
 
-__version__ = '1.2.0'
+__version__ = '1.2.1'
 
diff --git a/conans/client/build/cppstd_flags.py b/conans/client/build/cppstd_flags.py
index e5ca936c3..5435d63e6 100644
--- a/conans/client/build/cppstd_flags.py
+++ b/conans/client/build/cppstd_flags.py
@@ -26,7 +26,7 @@ def cppstd_flag(compiler, compiler_version, cppstd):
 def cppstd_default(compiler, compiler_version):
     default = {"gcc": _gcc_cppstd_default(compiler_version),
                "clang": _clang_cppstd_default(compiler_version),
-               "apple-clang": "gnu98",
+               "apple-clang": "gnu98",  # Confirmed in apple-clang 9.1 with a simple "auto i=1;"
                "Visual Studio": _visual_cppstd_default(compiler_version)}.get(str(compiler), None)
     return default
 
@@ -85,6 +85,11 @@ def _cppstd_apple_clang(clang_version, cppstd):
         v17 = "c++1z"
         vgnu17 = "gnu++1z"
 
+    if Version(clang_version) >= "9.1":
+        # Not confirmed that it didn't work before 9.1 but 1z is still valid, so we are ok
+        v17 = "c++17"
+        vgnu17 = "gnu++17"
+
     flag = {"98": v98, "gnu98": vgnu98,
             "11": v11, "gnu11": vgnu11,
             "14": v14, "gnu14": vgnu14,
diff --git a/conans/client/conf/__init__.py b/conans/client/conf/__init__.py
index 267416ced..96dd58553 100644
--- a/conans/client/conf/__init__.py
+++ b/conans/client/conf/__init__.py
@@ -65,7 +65,7 @@ compiler:
         version: ["3.3", "3.4", "3.5", "3.6", "3.7", "3.8", "3.9", "4.0", "5.0", "6.0"]
         libcxx: [libstdc++, libstdc++11, libc++]
     apple-clang:
-        version: ["5.0", "5.1", "6.0", "6.1", "7.0", "7.3", "8.0", "8.1", "9.0"]
+        version: ["5.0", "5.1", "6.0", "6.1", "7.0", "7.3", "8.0", "8.1", "9.0", "9.1"]
         libcxx: [libstdc++, libc++]
 
 build_type: [None, Debug, Release]
diff --git a/conans/client/migrations.py b/conans/client/migrations.py
index ef0ba6b31..27a86af1f 100644
--- a/conans/client/migrations.py
+++ b/conans/client/migrations.py
@@ -41,7 +41,7 @@ class ClientMigrator(Migrator):
         # VERSION 0.1
         if old_version is None:
             return
-        if old_version < Version("1.1.0-dev"):
+        if old_version < Version("1.2.1"):
             old_settings = """
 # Only for cross building, 'os_build/arch_build' is the system that runs Conan
 os_build: [Windows, WindowsStore, Linux, Macos, FreeBSD, SunOS]
@@ -82,9 +82,9 @@ compiler:
         libcxx: [libCstd, libstdcxx, libstlport, libstdc++]
     gcc:
         version: ["4.1", "4.4", "4.5", "4.6", "4.7", "4.8", "4.9",
-                  "5", "5.1", "5.2", "5.3", "5.4",
+                  "5", "5.1", "5.2", "5.3", "5.4", "5.5",
                   "6", "6.1", "6.2", "6.3", "6.4",
-                  "7", "7.1", "7.2"]
+                  "7", "7.1", "7.2", "7.3"]
         libcxx: [libstdc++, libstdc++11]
         threads: [None, posix, win32] #  Windows MinGW
         exception: [None, dwarf2, sjlj, seh] # Windows MinGW
@@ -93,13 +93,14 @@ compiler:
         version: ["8", "9", "10", "11", "12", "14", "15"]
         toolset: [None, v90, v100, v110, v110_xp, v120, v120_xp, v140, v140_xp, v140_clang_c2, LLVM-vs2014, LLVM-vs2014_xp, v141, v141_xp, v141_clang_c2]
     clang:
-        version: ["3.3", "3.4", "3.5", "3.6", "3.7", "3.8", "3.9", "4.0", "5.0"]
+        version: ["3.3", "3.4", "3.5", "3.6", "3.7", "3.8", "3.9", "4.0", "5.0", "6.0"]
         libcxx: [libstdc++, libstdc++11, libc++]
     apple-clang:
         version: ["5.0", "5.1", "6.0", "6.1", "7.0", "7.3", "8.0", "8.1", "9.0"]
         libcxx: [libstdc++, libc++]
 
 build_type: [None, Debug, Release]
+cppstd: [None, 98, gnu98, 11, gnu11, 14, gnu14, 17, gnu17]
 """
             self._update_settings_yml(old_settings)
 

Apple-clang 9.1 not supported
Please, add apple-clang 9.1 to supported platform. I had problem with compile missing libraries. I fixed it with manually edited ```.conan/settings.yml```

My CMake output:
```
-- The CXX compiler identification is AppleClang 9.1.0.9020039
```

Clang version: 
```sh
$ clang++ -v
Apple LLVM version 9.1.0 (clang-902.0.39.1)
Target: x86_64-apple-darwin17.5.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
```

Conan version:
```
$ conan -v
Conan version 1.2.0
```
diff --git a/conans/test/build_helpers/cpp_std_flags_test.py b/conans/test/build_helpers/cpp_std_flags_test.py
index b110bb3f4..7e7c1c5e4 100644
--- a/conans/test/build_helpers/cpp_std_flags_test.py
+++ b/conans/test/build_helpers/cpp_std_flags_test.py
@@ -136,6 +136,10 @@ class CompilerFlagsTest(unittest.TestCase):
         self.assertEquals(cppstd_flag("apple-clang", "9", "14"), '-std=c++14')
         self.assertEquals(cppstd_flag("apple-clang", "9", "17"), "-std=c++1z")
 
+        self.assertEquals(cppstd_flag("apple-clang", "9.1", "11"), '-std=c++11')
+        self.assertEquals(cppstd_flag("apple-clang", "9.1", "14"), '-std=c++14')
+        self.assertEquals(cppstd_flag("apple-clang", "9.1", "17"), "-std=c++17")
+
     def test_apple_clang_cppstd_defaults(self):
         self.assertEquals(cppstd_default("apple-clang", "2"), "gnu98")
         self.assertEquals(cppstd_default("apple-clang", "3"), "gnu98")

pip install -e .[dev]
parse_log_pytest
requirements.txt
nose pytest
apt-get update apt-get install -y gcc
3.6
conans/requirements.txt conans/requirements_dev.txt conans/requirements_server.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
astroid==1.6.6
attrs==22.2.0
beautifulsoup4==4.12.3
bottle==0.12.25
certifi==2021.5.30
charset-normalizer==2.0.12
codecov==2.1.13
colorama==0.3.9
-e git+https://github.com/conan-io/conan.git@e1e3cce13e69576f562296a1e6d64352e8e84ccd#egg=conan
coverage==4.2
deprecation==2.0.7
distro==1.1.0
fasteners==0.19
future==0.16.0
idna==3.10
importlib-metadata==4.8.3
iniconfig==1.1.1
isort==5.10.1
lazy-object-proxy==1.7.1
mccabe==0.7.0
mock==1.3.0
node-semver==0.2.0
nose==1.3.7
packaging==21.3
parameterized==0.8.1
patch==1.16
pbr==6.1.1
pluggy==1.0.0
pluginbase==0.7
py==1.11.0
Pygments==2.14.0
PyJWT==1.7.1
pylint==1.8.4
pyparsing==3.1.4
pytest==7.0.1
PyYAML==3.12
requests==2.27.1
six==1.17.0
soupsieve==2.3.2.post1
tomli==1.2.3
typing_extensions==4.1.1
urllib3==1.26.20
waitress==2.0.0
WebOb==1.8.9
WebTest==2.0.35
wrapt==1.16.0
zipp==3.6.0

name: conan
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:
      - astroid==1.6.6
      - attrs==22.2.0
      - beautifulsoup4==4.12.3
      - bottle==0.12.25
      - charset-normalizer==2.0.12
      - codecov==2.1.13
      - colorama==0.3.9
      - coverage==4.2
      - deprecation==2.0.7
      - distro==1.1.0
      - fasteners==0.19
      - future==0.16.0
      - idna==3.10
      - importlib-metadata==4.8.3
      - iniconfig==1.1.1
      - isort==5.10.1
      - lazy-object-proxy==1.7.1
      - mccabe==0.7.0
      - mock==1.3.0
      - node-semver==0.2.0
      - nose==1.3.7
      - packaging==21.3
      - parameterized==0.8.1
      - patch==1.16
      - pbr==6.1.1
      - pluggy==1.0.0
      - pluginbase==0.7
      - py==1.11.0
      - pygments==2.14.0
      - pyjwt==1.7.1
      - pylint==1.8.4
      - pyparsing==3.1.4
      - pytest==7.0.1
      - pyyaml==3.12
      - requests==2.27.1
      - six==1.17.0
      - soupsieve==2.3.2.post1
      - tomli==1.2.3
      - typing-extensions==4.1.1
      - urllib3==1.26.20
      - waitress==2.0.0
      - webob==1.8.9
      - webtest==2.0.35
      - wrapt==1.16.0
      - zipp==3.6.0
prefix: /opt/conda/envs/conan

conans/test/build_helpers/cpp_std_flags_test.py::CompilerFlagsTest::test_apple_clang_cppstd_flags
conans/test/build_helpers/cpp_std_flags_test.py::CompilerFlagsTest::test_apple_clang_cppstd_defaults conans/test/build_helpers/cpp_std_flags_test.py::CompilerFlagsTest::test_clang_cppstd_defaults conans/test/build_helpers/cpp_std_flags_test.py::CompilerFlagsTest::test_clang_cppstd_flags conans/test/build_helpers/cpp_std_flags_test.py::CompilerFlagsTest::test_gcc_cppstd_defaults conans/test/build_helpers/cpp_std_flags_test.py::CompilerFlagsTest::test_gcc_cppstd_flags conans/test/build_helpers/cpp_std_flags_test.py::CompilerFlagsTest::test_visual_cppstd_defaults conans/test/build_helpers/cpp_std_flags_test.py::CompilerFlagsTest::test_visual_cppstd_flags
conans/client/conf/__init__.py conans/client/build/cppstd_flags.py conans/__init__.py conans/client/migrations.py
conans/client/conf/__init__.py conans/client/build/cppstd_flags.py conans/__init__.py conans/client/migrations.py