360-day calendar

The 360-day calendar is a method of measuring durations used in financial markets, in computer models, in ancient literature, and in prophetic literary genres. It is based on merging the three major calendar systems into one complex clock, with the 360-day year as the average year of the lunar and the solar: [365.2425 (solar) + 354.3829 (lunar)] = 719.61 days. And 719.61 ÷ 2 = 359.8 days, rounding to 360. It is a simplification to a 360-day year, consisting of 12 months of 30 days each. To derive such a calendar from the standard Gregorian calendar, certain days are skipped.

Ancient calendars around the world initially used a 360 day calendar.

Romans initially used a calendar which had 360 days, with varying length of months.

The Rig Veda describes a calendar with twelve months and 360 days.

In the Mayan Long Count Calendar, the equivalent of the year, the tun, was 360 days.

A duration is calculated as an integral number of days between start date A and end date B. The difference in years, months and days are usually calculated separately:

There are several methods commonly available which differ in the way that they handle the cases where the months are not 30 days long, i.e. how they adjust dates:

equivalent to 30/360 BMA/PSA

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