Gcal 4.1: Moon phase

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G.2.1.9 Moon phase %[format]?[date] special texts

Gcal uses a very simple algorithm for detecting the Moon phase, which computes approximate values only. The Moon phase is always calculated for 0 o’clock Universal time (UTC/GMT). See Calendar option --time-offset=argument, how to change the base time for which the astronomical functions are calculated. The following Moon phase %[format]?[date] special texts are respected:

%O[date]

Is replaced by the Moon phase text of the current day of year, e.g.:

The text ‘Moon phase %O , %n’ will be expanded to
→ ‘Moon phase 94%+, 22-Dec-1996’, in case the actual system date is the 22nd December 1996.

The constructed Moon phase text consists of a percent value, which informs about the illuminated fraction of the Moon’s disk, and a trailing sign that tells something about the state of the Moon. A trailing ‘+’ sign indicates a waxing Moon, a ‘-’ sign a waning Moon, a ‘@’ sign indicates the Full Moon phase, and a ‘!’ sign the New Moon phase.

%>03*O[date]

Is replaced by the 3-digit Moon phase text with leading zeroes of the current day of year, e.g.:

The text ‘Moon phase %>03*O0@t+1 , %n+1’ will be expanded to
→ ‘Moon phase 098%+, 23-Dec-1996’, in case the actual system date is the 22nd December 1996.

The constructed Moon phase text consists of a percent value, which informs about the illuminated fraction of the Moon’s disk, and a trailing sign that tells something about the state of the Moon. A trailing ‘+’ sign indicates a waxing Moon, a ‘-’ sign a waning Moon, a ‘@’ sign indicates the Full Moon phase, and a ‘!’ sign the New Moon phase.

%Z[date]

Is replaced by the Moon phase text graphics of the current day of year, e.g.:

The text ‘Date %n %Z --- Moon phase %>03*O ~Text’ will be expanded to
→ ‘Date 08-Mar-1995 ’
→ ‘ ( @@@@@@’
→ ‘ ( @@@@@@@@@’
→ ‘ ( @@@@@@@@@@@’
→ ‘ ( @@@@@@@@@@@@’
→ ‘ ( @@@@@@@@@@@@@’
→ ‘( @@@@@@@@@@@@@’
→ ‘( @@@@@@@@@@@@@’
→ ‘ ( @@@@@@@@@@@@@’
→ ‘ ( @@@@@@@@@@@@’
→ ‘ ( @@@@@@@@@@@’
→ ‘ ( @@@@@@@@@’
→ ‘ ( @@@@@@@ --- Moon phase 041%+’
→ ‘Text’, in case the actual system date is the 8th March 1995.

See Fixed date option --moonimage-lines=number, how to change the size of a Moon phase text graphics.

A possibly specified format within this special text is ignored by Gcal.

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