#!/bin/sh

# This file is maintained using GNU Arch on
# http://mdcc.cx/arch/{archives}/2008-ad1810-stuff

# Copyright: © 2004 Joost van Baal
# This program is in the public domain.

# eerste-maandag-even-maand - waarschuw voor de eerte maandag van een even maand

# Usage: eerste-maandag-even-maand n < message
#  print message if current day is n days before eerste maandag even maand

# Written 2004-04

debug=''
# debug=YES # debug mode

n=$1

test $debug && echo >&2 finding out wether `date --date="+$n days" +%Y%m%d` will be first monday of an even month

# is later a monday?
#  ( %w: day of week (0..6);  0 represents Sunday )
if test 1 != `date --date="+$n days" +%w`
then
    test $debug && echo >&2 $n days later is not a monday
    exit 1
fi
# yes, it is

# is later in an even month?
case `date --date="+$n days" +%m` in
  01 | 03 | 05 | 07 | 09 | 11 )
    test $debug && echo >&2 $n days later is not in an even month
    exit 1
esac
# yes, it is

# is later the _first_ monday?
#  ( %e: blank-padded day of month (1...31) )
if test `date --date="+$n days" +%e` -lt 8
then
    # yes it is
    exit 0
else
    test $debug && echo >&2 $n days later is not the _first_ monday of an even month
    exit 1
fi