calendar

Calendar reads files for events, one event per line; and write to
standard output those events ocurring in the next seven days (counting
from today).

Each event should begin with a date pattern in the format
[[YYYY-[MM]]-DDWW[+N|-N].  The hyphen (-) that separates the values can
be replaced by a slash (/) or a period (.).  Several date patterns can
be supplied separated by a comma (,).

YYYY should be any year number.  MM should be a month number or a month
name (either complete or abbreviate, such as "April" or "Apr").  DD
should be the number of a day in the month.  WW should be the name of a
day in the week (either complete or abbreviate).  Either DD or WW (or
both) must be supplied.

The date pattern can be followed by +N or -N to specify the week on the
month (for example Sun+2 is the second Sunday in the month, Mon-3 is
the third from last Monday in the month).

For example, consider the following input.

	# holidays
	01/01      New Year's day
	05/01      Labor Day
	07/25      Generic holiday
	12/25      Christmas
	May/Sun+2  Mother's day
	13Fri      Friday the 13th
	
	# classes
	Mon,Wed Java Class
	Tue,Thu Algebra Class
	Tue,Thu Operating Systems Class
	Tue,Thu Computer Network Class

If today were 09 March 2021, then running calendar on this input would
print the following:

	Sunday     09 May 2021
	        Mother's day
	Monday     10 May 2021
	        Java Class
	Tuesday    11 May 2021
	        Algebra Class
	        Computer Network Class
	        Operating Systems Class
	Wednesday  12 May 2021
	        Java Class
	Thursday   13 May 2021
	        Algebra Class
	        Computer Network Class
	        Operating Systems Class
	Friday     14 May 2021
	Saturday   15 May 2021

This software is in public domain and is provided AS IS, with NO WARRANTY.