Which calendar type is Lunar New Year based on in many East Asian traditions?

In many East Asian traditions, Lunar New Year is based on a lunisolar calendar.

A lunisolar calendar uses the Moon to define its months but also keeps the calendar synchronized with the solar year. Lunar months are roughly 29 or 30 days long, so twelve of them fall short of a full solar year. To correct the drift, an extra intercalary month is inserted periodically; this is why some traditional years have thirteen months.

This system allows festivals to follow both visible lunar cycles and the seasons. In the traditional Chinese calendar, New Year generally begins on the second new moon after the winter solstice, though exact rules and regional calendars can differ. Chinese New Year, Korean Seollal, and Vietnamese Tết are related examples.

The phrase “Lunar New Year” can therefore be misleading. The Islamic calendar is purely lunar and moves through the seasons, while the Gregorian and Julian calendars are solar calendars. East Asian New Year traditions are better described as lunisolar, even when everyday English uses the shorter label.