I'm opening a new issue because I think it's different from what I mentioned in MONGOID-2691.

I have Mongoid.use_activesupport_time_zone: false

>> l.shippings << Time.now
=> [2013-01-24 15:47:06 -0500]
>> l.save
=> true
>> l.reload
>> l.shippings
=> [2013-01-24 20:47:06 UTC]


>> l.created_at
=> 2013-01-29 08:49:45 -0500

A field declared as Time (created_at) demongoize itself into a localized Time (although not an ActiveSupport::TimeWithZone), but not from withing an array (shippings). I would expect it to have the same behavior.