Why does Maya have three calendars?

The Maya accurately calculated the length of the solar year as 365.2420 days, and the modern people calculated it as 365.2422 days, according to the Mayan calendar.

The error is only 0.0002 days, which means that the error is only one day in 5000 years.

Lunar ephemeris

Venus calendar. It took the Mayans 384 years to observe and calculate the 584-day Venus calendar year. Modern people estimate that it is 583.92 days, with a daily error of less than 12 second and only 6 minutes per month.

Zorkin

Every year for 260 days, the images of 20 gods and the numbers of 13 from 0 to 12 are continuously combined and circulated, just like heavenly stems and earthly branches in China, and 260 combined icons are obtained, representing 260 days.