How to use Active Support core extensions

Since using Rails should handle this automatically I'm going to assume you're trying to add Active Support to a non-Rails script.

Read "How to Load Core Extensions".

Active Support's methods got broken into smaller groups in Rails 3, so we don't end up loading a lot of unneeded stuff with a simple require 'activesupport'. Now we have to do things like

require 'active_support/core_ext/object/blank'

If you don't care about granularity, you can choose to load bigger chunks. If you want everything in one big gulp use...

For 1.9.2:

rvm 1.9.2
irb -f
irb(main):001:0> require 'active_support/all'
=> true
irb(main):002:0> 1.week.ago
=> 2010-11-14 17:56:16 -0700
irb(main):003:0> 

For 1.8.7:

rvm 1.8.7
irb -f
irb(main):001:0> require 'rubygems'
=> true
irb(main):002:0> require 'active_support/all'
=> true
irb(main):003:0> 1.week.ago
=> Sun Nov 14 17:54:19 -0700 2010
irb(main):004:0> 

You can granularly add libraries via the already mentioned

require 'active_support/core_ext/some_class/some_file'

There is also another level up where you can

require 'active_support/core_ext/some_class'

But, at the moment, this is unfortunately not available for Time, Date and DateTime.

A way around this is to require 'active_support/time' which will give you Time, Date and DateTime which would solve the OP was asking for without requiring everything.

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My Rails patch, which adds active_support/core_ext/date and date_time, made it into Rails v4.0.0, so now you can require these individually. YAY!