Today is on the Gregorian Calendar.
Today's
The MEOW Community Cooperation Blog's 'MEOW Date' uses a dating system which combines The World Calendar and The Holocene Calendar:
The World Calendar Association
On the Hololcene Era:
A very complete page via The WayBack Machine on HE
and
http://en.wikipedia.org/wiki/Holocene_calendar
Well-explained with the daily date in JavaScript