DateTime

One thing I dislike with Rails module and documentation: never mention the method min,sec, etc… Just figured them out

where one or more of the elements have been changed according to the options parameter. The time options (hour, minute, sec) reset cascadingly, so if only the hour is passed, then minute and sec is set to 0. If the hour and minute is passed, then sec is set to 0.

Full article: http://api.rubyonrails.org/classes/DateTime.html