Datamapper DataMapper

In MySQL, datetime columns do not retain any time-zone information unlike for example, PostGreSQL which saves the TZ. MySQL instead assumes that the time is local and adjusts it to UTC before inserting (http://tinyurl.com/d9syqn). This will causes a problem if you're working exclusively with UTC timezones rather than local. MySQL, with no concept of TZ, will attempt to convert an a UTC timestamp to UTC which will obviously end up writing the wrong datetime.

Date(times) are always set to the current time zone while maintaining the date information in the database, this results in an incorrect time (UTC elements with a local time zone).

class Article
  ...
  property :created_at, Time
end


%irb%

Article.create(:created_at => Time.now.utc - 1.hour)

Article.all(:created_at.lte => Time.now.utc) -> [#<Article id=1 created_at=Thu Jan 29 01:30:54 -0700 2009>]  

Article.all.find_all {|a| a.created_at <= Time.now.utc} -> [] 

Article.first.created_at < Time.now.utc -> false
(Time.utc *Article.first.created_at.to_a) < Time.now.utc -> true