Date and Time Calculations in Rails

Calculating dates and times has always been a challenge for programmers. How many days until the next New Years Eve party (oh, did you forget 2008 is a leap year)? How long ago was the last backup (convert that to GMT, please)? What day of the week is 19 days, 42 hours, and 374 minutes from now (and how many milliseconds is that again)? And don’t even get me started on Y2K!