Time in Rails

Not much different...

time_now = Time.now
time_one_week_from_now = time_now + 60 * 60 * 24 * 7

http://www.rubycentral.com/book/ref_c_time.html
http://www.ruby-doc.org/stdlib/libdoc/date/rdoc/classes/DateTime.html

There's some other date helpers in rails that may be useful too
http://rubyonrails.com/rails/classes/ActionView/Helpers/DateHelper.html