cheat sheets.

>> 3.days.ago.to_s(:db)

Formats:
  :db
    "%Y-%m-%d %H:%M:%S" (ie: "2006-12-04 19:00:26")
  :long
    "%B %d, %Y %H:%M" (ie: "December 04, 2006 19:00")
  :rfc822
    "%a, %d %b %Y %H:%M:%S %z" (ie: "Mon, 04 Dec 2006 19:00:26 -0700")
  :short
    "%d %b %H:%M" (ie: "04 Dec 19:00")
  :time
    "%H:%M" (ie: "19:00")

Add your own:
  Time::DATE_FORMATS[:mine] = '%Y%m%d%M%S'
   >> Time.new.to_s(:mine)
   => "200612040026"