How to create a new DateTime object in a specific time zone (preferably the default time zone of my app, not UTC)?
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I have set the time zone in `/config/application.rb`, and I expect all times generated in my app to be in this time zone by default, yet when I create a new `DateTime` object (using `.new`), it creates it in `GMT`. How can I get it to be in my app's time zone?

**/config/application.rb**

    config.time_zone = 'Pacific Time (US & Canada)'

**irb**

    irb> DateTime.now
    => Wed, 11 Jul 2012 19:04:56 -0700 

    irb> mydate = DateTime.new(2012, 07, 11, 20, 10, 0)
    => Wed, 11 Jul 2012 20:10:00 +0000                    # GMT, but I want PDT

Using `in_time_zone` doesn't work because that just converts the GMT time to PDT time, which is the wrong time:

    irb> mydate.in_time_zone('Pacific Time (US & Canada)')
    => Wed, 11 Jul 2012 13:10:00 PDT -07:00               # wrong time (I want 20:10)
