#! /bin/echo Source_this_file:
# Wed Feb  6 12:32:34 EST 2002
# /usr/local/bin/datefuncs
# Copyright 2002,2003 Chris F.A. Johnson
# Released under the terms of the GNU General Public License

valid_date() {
    order=dmy
    case $1 in
	-dmy) order=dmy; shift ;; ## default
	-mdy) order=mdy; shift ;;
	-ymd) order=ymd; shift ;;
    esac

    ofs=$IFS
    IFS="$IFS-./"
    set $*
    case $order in
	dmy) v_day=$1
	     v_month=$2
	     v_year=$3
	     ;;
	mdy) v_month=$1
	     v_day=$2
	     v_year=$3
	     ;;
	ymd) v_month=$2
	     v_day=$3
	     v_year=$1
	     ;;
    esac
    IFS=$ofs

    case $v_year in
	"") v_year=`date +%Y` ;;
	*[!0-9]*) echo "Year $v_year contains a non-numeric character" >&2
                  return 1 ;;
    esac

    case $v_month in
       ## allow non-padded months
       [1-9]|\
       0[1-9]|\
       1[012]) ;;
       *) echo "Invalid month: $v_month" >&2
          return 1
          ;;
   esac

   case $v_day in
       ## allow non-padded days
       [1-9]|\
       0[1-9]|\
       1[0-9]|\
       2[0-8]) ;; ## if 28 or less, day is OK
       [23][0-9]) days_in_month $v_month $v_year
          [ $day -le $_DAYS_IN_MONTH ] || {
	      echo "Invalid day: $v_day" >&2
	      return 1
          }
          ;;
        *) echo "Invalid day: $v_day" >&2
           return 1
	   ;;
   esac
}

days_in_month() { ## USAGE: days_in_month [month [year]]
    if [ -n "$1" ] 
    then
	dim_m=$1
        dim_y=$2
    else
	eval `date "+dim_m=%m dim_y=%Y"`
    fi
    case $dim_m in
        *9|*4|*6|11) _DAYS_IN_MONTH=30 ;; ## 30 days hath September...
        1|01|3|03|*5|*7|*8|10|12) _DAYS_IN_MONTH=31 ;;
        2|02) is_leap_year ${dim_y:-`date +%Y`} && _DAYS_IN_MONTH=29 || _DAYS_IN_MONTH=28 ;;
    esac
    [ ${SILENT_FUNCS:-0} -eq 1 ] || echo $_DAYS_IN_MONTH
}

is_leap_yr() { ## USAGE: is_leap_yr [year]
    isl_year=${1:-`date +%Y`}
    [ $(( $isl_year % 400)) -eq 0 -o \
        \( $(( $isl_year % 4)) -eq 0 -a $(( $isl_year % 100)) -ne 0 \) ] && {
                _IS_LEAP_YEAR=1
	        return 0
		} ||{
                _IS_LEAP_YEAR=0
	        return 1
		}
}

is_leap_year() { ## USAGE: is_leap_year [year]
    isl_year=${1:-`date +%Y`}
    case $isl_year in
        *0[48] |\
        *[2468][048] |\
        *[13579][26] |\
        *[13579][26]0|\
        *[2468][048]00 |\
        *[13579][26]00 ) _IS_LEAP_YEAR=1
	                 return 0 ;;
        *) _IS_LEAP_YEAR=0
	   return 1 ;;
    esac
}

monthnum() {
    case $1 in
        1|01|[Jj][aA][nN]) _MONTHNUM=1 ;;
        2|02|[Ff][Ee][Bb]) _MONTHNUM=2 ;;
        3|03|[Mm][Aa][Rr]) _MONTHNUM=3 ;;
        4|04|[Aa][Pp][Rr]) _MONTHNUM=4 ;;
        5|05|[Mm][Aa][Yy]) _MONTHNUM=5 ;;
        6|06|[Jj][Uu][Nn]) _MONTHNUM=6 ;;
        7|07|[Jj][Uu][Ll]) _MONTHNUM=7 ;;
        8|08|[Aa][Uu][Gg]) _MONTHNUM=8 ;;
        9|09|[Ss][Ee][Pp]) _MONTHNUM=9 ;;
        10|[Oo][Cc][Tt]) _MONTHNUM=10 ;;
        11|[Nn][Oo][Vv]) _MONTHNUM=11 ;;
        12|[Dd][Ee][Cc]) _MONTHNUM=12 ;;
        *) return 5 ;;
    esac
    [ ${SILENT_FUNCS:-0} -eq 1 ] || echo ${_MONTHNUM}
}

#<a name="monthname"></a>
monthname() {
    case $1 in
	1|01|[Jj][aA][nN]) _MONTHNAME=January ;;
        2|02|[Ff][Ee][Bb]) _MONTHNAME=February ;;
	3|03|[Mm][Aa][Rr]) _MONTHNAME=March ;;
	4|04|[Aa][Pp][Rr]) _MONTHNAME=April ;;
	5|05|[Mm][Aa][Yy]) _MONTHNAME=May ;;
	6|06|[Jj][Uu][Nn]) _MONTHNAME=June ;;
	7|07|[Jj][Uu][Ll]) _MONTHNAME=July ;;
	8|08|[Aa][Uu][Gg]) _MONTHNAME=August ;;
	9|09|[Ss][Ee][Pp]) _MONTHNAME=September ;;
	10|[Oo][Cc][Tt]) _MONTHNAME=October ;;
	11|[Nn][Oo][Vv]) _MONTHNAME=November ;;
	12|[Dd][Ee][Cc]) _MONTHNAME=December ;;
	*) return 5 ;;
    esac
    [ ${SILENT_FUNCS:-0} -eq 1 ] || echo ${_MONTHNAME}
}

daynum() {
    case $1 in
	0|00|7|07|[Ss][Uu][Nn]) _DAYNUM=0 ;;
        1|01|[Mm][Oo][nN]) _DAYNUM=1 ;;
	2|02|[Tt][Uu][Ee]) _DAYNUM=2 ;;
	3|03|[Ww][Ee][Dd]) _DAYNUM=3 ;;
	4|04|[Tt][Hh][Uu]) _DAYNUM=4 ;;
	5|05|[Ff][Rr][Ii]) _DAYNUM=5 ;;
	6|06|[Ss][Aa][Tt]) _DAYNUM=6 ;;
	*) return 5 ;;
    esac
    [ ${SILENT_FUNCS:-0} -eq 1 ] || echo ${_DAYNUM}
}

dayname() {
echo ${1%${1#???}}
    case ${1%${1#???}} in
	0|00|7|07|[Ss][Uu][Nn]) _DAYNAME=Sunday ;;
        1|01|[Mm][Oo][nN]) _DAYNAME=Monday ;;
	2|02|[Tt][Uu][Ee]) _DAYNAME=Tuesday ;;
	3|03|[Ww][Ee][Dd]) _DAYNAME=Wednesday ;;
	4|04|[Tt][Hh][Uu]) _DAYNAME=Thursday ;;
	5|05|[Ff][Rr][Ii]) _DAYNAME=Friday ;;
	6|06|[Ss][Aa][Tt]) _DAYNAME=Saturday ;;
	*) return 5 ;;
    esac
    [ ${SILENT_FUNCS:-0} -eq 1 ] || echo ${_DAYNAME}
}

dayofweek() {
    _y=$1
    _m=$2
    _d=$3
    case $_m in
	1|5) _t=0 ;;
	2|6) _t=3 ;;
	3|11) _t=2 ;;
	4|7) _t=5 ;;
	8) _t=1 ;;
	9|12) _t=4 ;;
	10) _t=6 ;;
    esac
    [ $_m -lt 3 ] && _y=$(( $_y - 1 ))
    _DAYOFWEEK=$(( ($_y + $_y/4 - $_y/100 + $_y/400 + $_t + $_d) % 7 ))
    [ ${SILENT_FUNCS:-0} -eq 1 ] || echo $_DAYOFWEEK
}

case $BASH_VERSION in
    [2-9].*|[1-9][0-9].*)
             export -f valid_date days_in_month is_leap_yr is_leap_year
             export -f monthnum monthname daynum dayname dayofweek
	     ;;
esac