What Long Count unit equals 20 days?

The Long Count unit equal to 20 days is the winal, also spelled uinal. It contains 20 kʼin, the Maya unit for one day.

The winal belongs to the Long Count’s distinctive counting system. Eighteen winals make one tun, or 360 days, rather than the 400 days expected from a completely base-20 system. This adjustment approximated the length of the Maya agricultural year while preserving a largely vigesimal structure.

Larger units build upward from the tun: 20 tuns make a kʼatun, and 20 kʼatuns make a bʼakʼtun. That is why a Long Count date such as 13.0.0.0.0 records nested periods rather than ordinary calendar months.

A common mix-up is confusing the winal with the tun. The winal is only 20 days; the tun is 18 winals, or 360 days. The Maya also used the 260-day Tzolkʼin and 365-day Haabʼ calendars alongside the Long Count.