# (emacs)Mayan Calendar

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Converting from the Mayan Calendar
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Here are the commands to select dates based on the Mayan calendar:

`g m l'
Move to a date specified by the long count calendar
(`calendar-goto-mayan-long-count-date').

`g m p t'
Move to the previous occurrence of a place in the tzolkin calendar
(`calendar-previous-tzolkin-date').

`g m n t'
Move to the next occurrence of a place in the tzolkin calendar
(`calendar-next-tzolkin-date').

`g m p h'
Move to the previous occurrence of a place in the haab calendar
(`calendar-previous-haab-date').

`g m n h'
Move to the next occurrence of a place in the haab calendar
(`calendar-next-haab-date').

`g m p c'
Move to the previous occurrence of a place in the calendar round
(`calendar-previous-calendar-round-date').

`g m n c'
Move to the next occurrence of a place in the calendar round
(`calendar-next-calendar-round-date').

To understand these commands, you need to understand the Mayan
calendars.  The "long count" is a counting of days with these units:

1 kin = 1 day   1 uinal = 20 kin   1 tun = 18 uinal
1 katun = 20 tun   1 baktun = 20 katun

Thus, the long count date 12.16.11.16.6 means 12 baktun, 16 katun, 11
tun, 16 uinal, and 6 kin.  The Emacs calendar can handle Mayan long
count dates as early as 7.17.18.13.1, but no earlier.  When you use the
`g m l' command, type the Mayan long count date with the baktun, katun,
tun, uinal, and kin separated by periods.

The Mayan tzolkin calendar is a cycle of 260 days formed by a pair of
independent cycles of 13 and 20 days.  Since this cycle repeats
endlessly, Emacs provides commands to move backward and forward to the
previous or next point in the cycle.  Type `g m p t' to go to the
previous tzolkin date; Emacs asks you for a tzolkin date and moves point
to the previous occurrence of that date.  Similarly, type `g m n t' to
go to the next occurrence of a tzolkin date.

The Mayan haab calendar is a cycle of 365 days arranged as 18 months
of 20 days each, followed a 5-day monthless period.  Like the tzolkin
cycle, this cycle repeats endlessly, and there are commands to move
backward and forward to the previous or next point in the cycle.  Type
`g m p h' to go to the previous haab date; Emacs asks you for a haab
date and moves point to the previous occurrence of that date.
Similarly, type `g m n h' to go to the next occurrence of a haab date.

The Maya also used the combination of the tzolkin date and the haab
date.  This combination is a cycle of about 52 years called a *calendar
round*.  If you type `g m p c', Emacs asks you for both a haab and a
tzolkin date and then moves point to the previous occurrence of that
combination.  Use `g m p c' to move point to the next occurrence of a
combination.  Emacs signals an error if the haab/tzolkin date you have
typed is impossible.

Emacs uses strict completion (Note: Completion.) whenever it asks
you to type a Mayan name, so you don't have to worry about spelling.

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