Chronic is a natural language (English only, at present, I think) time and date parser written entirely in Ruby. It supports a staggering number of different ways of expressing the date and time. For example:

tomorrow
this monday 07:30
may 15th
tomorrow morning
yesterday at 9:00
tomorrow at 11pm
wednesday last week

Time.parse already does a great job, but this goes a step further. You can install chronic quickly with gem install chronic.