uninitialized constant ActiveSupport::CoreExtensions::Date::Calculations - ruby

Question

I'm new to ruby, rails and mysql.
My operating system is Ubuntu 13.04, the version of ruby is 1.9.3p194 (2012-04-20 revision 35410) [x86_64-linux] and the version of rails is 3.2.13.
When I executed this command: rake db:migrate --trace, I encountered such errors:
rake aborted!
uninitialized constant ActiveSupport::CoreExtensions::Date::Calculations
/usr/lib/ruby/vendor_ruby/active_support/core_ext/date.rb:8:in `<class:Date>'
/usr/lib/ruby/vendor_ruby/active_support/core_ext/date.rb:6:in `<top (required)>'
/var/lib/gems/1.9.1/gems/date_time_precision-0.5.3/lib/date_time_precision/lib.rb:4:in `block in <top (required)>'
/var/lib/gems/1.9.1/gems/date_time_precision-0.5.3/lib/date_time_precision/lib.rb:2:in `each'
/var/lib/gems/1.9.1/gems/date_time_precision-0.5.3/lib/date_time_precision/lib.rb:2:in `<top (required)>'
/var/lib/gems/1.9.1/gems/date_time_precision-0.5.3/lib/date_time_precision/patch.rb:1:in `<top (required)>'
/var/lib/gems/1.9.1/gems/date_time_precision-0.5.3/lib/date_time_precision.rb:1:in `<top (required)>'
/var/lib/gems/1.9.1/gems/bundler-1.5.2/lib/bundler/runtime.rb:76:in `require'
/var/lib/gems/1.9.1/gems/bundler-1.5.2/lib/bundler/runtime.rb:76:in `block (2 levels) in require'
/var/lib/gems/1.9.1/gems/bundler-1.5.2/lib/bundler/runtime.rb:72:in `each'
/var/lib/gems/1.9.1/gems/bundler-1.5.2/lib/bundler/runtime.rb:72:in `block in require'
/var/lib/gems/1.9.1/gems/bundler-1.5.2/lib/bundler/runtime.rb:61:in `each'
/var/lib/gems/1.9.1/gems/bundler-1.5.2/lib/bundler/runtime.rb:61:in `require'
/var/lib/gems/1.9.1/gems/bundler-1.5.2/lib/bundler.rb:131:in `require'
/home/xye/Documents/Work/config/application.rb:14:in `<top (required)>'
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
/home/xye/Documents/Work/Rakefile:5:in `<top (required)>'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/rake_module.rb:25:in `load'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/rake_module.rb:25:in `load_rakefile'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:583:in `raw_load_rakefile'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:89:in `block in load_rakefile'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:160:in `standard_exception_handling'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:88:in `load_rakefile'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:72:in `block in run'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:160:in `standard_exception_handling'
/var/lib/gems/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:70:in `run'
/var/lib/gems/1.9.1/gems/rake-10.0.3/bin/rake:33:in `<top (required)>'
/usr/local/bin/rake:23:in `load'
/usr/local/bin/rake:23:in `<main>'
It's quite weird, and I don't know how to handle it. Any ideas?

Answer 1

The gem called date_time_precision is conflicting with active support.
From the date_time_precision docs:
Gem Compatibility
Sometimes other gems will use the Date/Time class in ways that don't preserve precision. If you want to use the DateTimePrecision gem with these gems, any compatibility issues will most likely need to be patched within DateTimePrecision itself. This is because DateTimePrecision makes some modifications to how the core Date/Time classes work. (For example, by allowing nil values to be passed to constructors.)
This gem should work with Rails/ActiveSupport 2, 3, and 4 (but perhaps missing some edge cases).
So far, the following gems are on the compatibility watch list:
[.] ActiveSupport
[x] Virtus
[x] Coercible
[ ] Chronic
[ ] Timeliness
[ ] Timecop
[ ] delocalize
You should remove this gem if you are not confident in fixing it yourself.