Arvelie is an alphabetic date format.

The Arvelie calendar has 26 months of 14 days each.

Each month has 2 weeks of 7 days, and each month's name is one of the 26 letters of the alphabet. The 365th day of the year is the Year Day(+00), preceded by the Leap Day(+01) on leap years.

The purpose of this special calendar is to record daily activity logs starting at year 0 when the tracking started. For example, this wiki was initiated in 2006, which is its year 0. The arvelie date 13A05, is equivalent to January 6th of the 14th year.

01D07 2007-02-18
02A00 2008-01-01
14C01 2009-01-29
03+00 2010-12-31

To calculate the day of the year, convert the month's letter to a value, starting with 0 for A, multiply by 14 and add the day of the month. For example, J05 is equal to (+ 5 (* 9 14)), or 131.

Swatch Beats

Time is measured by earth rotation around the sun, where 0 beats is midnight, 500 beats is mid-day, 1000 is right before midnight again.

• Swatch internet time (Wikipedia)