These dates are from the Calendar Round, a method of dating in which one day is unique from 18979 others. The two parts of the date, 4 Ahau and 8 Cumhu come from the Tzolkin 260 calendar and the Haab 365 day calendar.

Since Calendar Round dates can only distinguish within 18980 days, equivalent to around 52 solar years, the cycle repeats roughly once each lifetime, and thus, a much more refined method of dating was needed if their history was to be recorded accurately.

The Long Count employs the use of number series, roughly base 20 and is constructed by counting whole number of days alone. The Mayan name for a day was kin; twenty of these kins are known as a uinal; eighteen uinals make one tun; twenty tuns are known as a katun, twenty katuns make a baktun. (Four higher order cycles but rarely used are known as Pictun, Calabtun, Kinchiltun, and Alautun.)

Days	Long Count Periods	Long Count	Approx. Solar Years	Tuns
1	= 1 Kin
20	= 20 Kin	= 1 Uinal
360	= 18 Uinal	= 1 Tun	~ 1	1
7 200	= 20 Tun	= 1 Katun	~ 20	20
144 000	= 20 Katun	= 1 Bactun	~ 395	400

Table of contents

1 Calculating Long Count Dates 1.1 Calculating the Tzolkin date portion of the Long Count 1.2 Calculating the Haab date portion of the Long Count 2 See also: 3 External Link

Calculating Long Count Dates

Long count dates list number of the highest order period first (Baktun) and then the number of each successively smaller order periods until the number of days (kin) are listed. Then the Calendar Round date is given.

A typical Calendar Round date is 9.12.2.0.16 5 Cib 14 Yaxkin . One can check whether this date is correct by the following calculation.

It is perhaps easier to find out how many days there are since 4 Ahau 8 Cumhu, and show how the date 5 Cib 14 Yaxkin is derived.

9	x 144000	= 1296000
12	x 7200	= 86400
2	x 360	= 720
0	x 20	= 0
16	x 1	= 16
	Total days	= 1383136 kin

Calculating the Tzolkin date portion of the Long Count

The Tzolkin date is counted forward from 4 Ahau. To calculate the numerical portion of the Tzolkin date, we must add 4 to the divide total number of days by 13.

(4 + 1383136) / 13 = 106395 and 5/13

This means that 106395 complete 13 day cycles have been completed, and the numerical portion of the Tzolkin date is 5.

To calculate the day, we divide the total number of days in the long count by 20 since there are twenty day names.

1383136 / 20 = 69156 and (16/20)

This means 16 day names must be counted from Ahau. This gives Cib. Therefore, the Tzolkin date is 5 Cib.

Calculating the Haab date portion of the Long Count

The Haab date 8 Cumhu is the ninth day of the eighteenth month. Since there are twenty days per month, there are eleven days remaining in Cumhu. The nineteeth and last month of the Haab year contains only five days, there are sixteen days until the end of the Haab year.

If we subtract 16 days from the total, we can then find how many complete Haab years are contained.

1383136 - 16 = 1383120

Dividing by 365, we have

1383120 / 365 = 3789 and (135/365)

Therefore, 3789 complete Haab have passed, with 135 days into the new Haab.

We then find which month the day is in. Dividing the remainder 135 days by 20, we have six complete months, plus 15 remainder days. So, the date in the Haab lies in the seventh month, which is Yaxkin. The fifteenth day of Yaxkin is 14, thus the Haab date is 14 Yaxkin.

So the date of the long count date 9.12.2.0.16 5 Cib 14 Yaxkin is confirmed.

See also:

• Maya civilisation
• Maya calendar