Đại lịch (ICT)

Overview

The Đại lịch calendar is a traditional observational lunisolar calendar of Vietnam. It is derived from the Chinese lunisolar calendar and shares many of the same elements, but it is set to Vietnamese time, meaning on rare occasions the two calendars can temporarily be significantly offset, only to realign again later.

It features 12 months of 29 or 30 days with a leap month on average every 2-3 years.

The Đại lịch calendar also follows a similar 12 Earthly Branches (Vietnamese Zodiac) theme for each year, though a few of the animals are different from the Chinese calendar.

This calendar uses the same epoch as the Gregorian calendar and may not reflect historic epochs. Similarly, the calendar hasn't always been set to Vietnamese time, changing back from Chinese time in the mid-20th century, so dates before that are likely to be incorrect.

Info

Accuracy

This calendar relies on the same calculations as the Chinese Lunisolar Calendar, though using midnight in Vietnam as the start of the say. Thus, it may vary mildly or significantly from the Chinese calendar. This may or may not itself be accurate, but the result should be relatively close to reality.

Source

Some general information was taken from the Wikipedia article for this calendar, but the general calculation is derived from the Chinese lunisolar calendar.