Update: Dates in this article have been changed for the year 2020.

Lunar New Year kicks off Saturday as one of the most important holidays in Vietnam, South Korea, China and other Asian countries. Typically, it starts on the second new moon after winter solstice.

On the Gregorian calendar, the civil calendar used in most countries, including the United States, the Lunar New Year changes every year, as do the dates of holidays like Rosh Hashana, Diwali and Ramadan.

It can be easy to think of a calendar as a scientific given, or a reflection of the laws of the universe. In fact, as these holidays remind us, there are as many ways to track time as there are cultures and languages. Each calendar reveals something about how the people who created it relate to the world around them while also preserving rich cultural identities and memories.

Most time-keeping traditions track the movement of the sun, moon and stars. Others consider seasonal events, like the autumnal swarming of sea worms, used to orient each year in the Trobriand Islands off New Guinea, or the flowering of immortelle trees into hundreds of tiny vermilion flames, which marks the start of the dry season in Trinidad.