diff --git a/lib/bank_time/calendar.rb b/lib/bank_time/calendar.rb
index <HASH>..<HASH> 100644
--- a/lib/bank_time/calendar.rb
+++ b/lib/bank_time/calendar.rb
@@ -32,7 +32,7 @@ module BankTime
     # Return true if the date given is a business day (typically that means a
     # non-weekend day) and not a holiday.
     def business_day?(date)
-      date = date.to_date if date.is_a?(Time)
+      date = date.to_date
       return false unless business_days.include?(date.strftime('%a').downcase)
       return false if holidays.include?(date)
       true
diff --git a/spec/calendar_spec.rb b/spec/calendar_spec.rb
index <HASH>..<HASH> 100644
--- a/spec/calendar_spec.rb
+++ b/spec/calendar_spec.rb
@@ -102,6 +102,11 @@ describe BankTime::Calendar do
         let(:day) { date_class.parse("Tuesday 1st Jan, 2013") }
         it { should be_false }
       end
+
+      context "when given a datetime that is not a business day" do
+        let(:day) { DateTime.parse("9am, Tuesday 1st Jan, 2013") }
+        it { should be_false }
+      end
     end
 
     describe "#roll_forward" do
Fix business_day? so it works with DateTimes