Haven't played much with dates and Ruby, but from date.rb's rdoc
(http://www.ruby-doc.org/stdlib/libdoc/date/rdoc/files/date_rb.html):
"DateTime objects support a simple representation of time zones. ...
This simple representation of time zones does not take into account
the common practice of Daylight Savings Time or Summer Time."

  And also: "The Date class does not support time zone offsets, in
that there is no way to create a Date object with a time zone."