`` Written by D. Sureau in Scriptol
`` from a public domain C source.
`` I can't garantee all dates are rights...
`` www.scriptol.org - Public domain.


constant int ISO_CAL = 0

array days      = array(31, 28, 31, 30, 31, 30,  31, 31, 30, 31, 30, 31)
array daynames  = array("Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun")
array months    = array("January", "February", "March", "April",
                        "May", "June", "July", "August",
                        "September", "October", "November", "December")

void usage()
	print "Usage: cal month year"
	print "where: month 1 - 12"
	print "       year 1 - 99 or 1800 - 3000"
	exit(-1)
return

boolean isLeap(int yr)
	boolean x = (yr mod 400) = 0
	boolean y = (yr mod 4) = 0
	boolean z = (yr mod 100) <> 0
return x or (y and z)


int monthsToDays(int month)
return (month * 3057 - 3007) / 100


int yearsToDays(int yr)
return (yr * 365) + (yr / 4) - (yr / 100) + (yr / 400)


int scalarFromYMD(int yr, int mo, int day)
	int scalar
	scalar = day + monthsToDays(mo)
	if mo > 2                          // adjust if past February
		if isLeap(yr)
			scalar - 1
		else
			scalar - 2
		/if
	/if
	scalar + yearsToDays(yr - 1)
return scalar


int today()

	int y, m, d
	dict x = localtime()
	y = x["tm_year"]
	m = x["tm_mon"]
	d = x["tm_mday"]

return scalarFromYMD(y + 1900, m + 1, d)



int, int, int scalarToYMD(int scalar)

	int  n = int( ((scalar * 400) / 146097) )

	while yearsToDays(n) < scalar
		n + 1
	/while

	int yr = n
	n = int(scalar - yearsToDays(n - 1))
	if n > 59
		n + 2
		if isLeap(yr)
			if n >  62
				n - 1
			else
				n - 2
			/if
		/if
	/if

	int mo = ((n * 100) + 3007) / 3057
	int day = n - monthsToDays(mo)

return yr, mo, day


int main(int argc, array argv)

	int day, firstDay, numdays
	int i, j
	int yr, mo, dy
	int thisMonth, thisYear, thisDay

	thisYear, thisMonth, thisDay = scalarToYMD(today())

	if argc not in 1..3 let usage()

	`` The month, or the month and the year may be given,
	`` the default is the current month at start.

	if argc
	= 3:
		yr = argv[2].toInt()
		mo = argv[1].toInt()
	= 2:
		if argv[1] in ("?", "/h", "-?", "-h", "--help") let usage()
		mo = argv[1].toInt()
		yr, i, j = scalarToYMD(today())
	else
		yr, mo, dy = scalarToYMD(today())
	/if

	if not (mo in 1..12) let usage()

	if yr < 100 let yr + 2000

	if yr not in 1800..3000 let usage()

	for i in 0 .. 2

	if mo < 1
		mo = 12
		yr - 1
	/if

	if mo > 12
		mo = 1
		yr + 1
	/if

	numdays = days[mo - 1]

	`` each 4 years february is 29 days long

	if (mo = 2) and isLeap(yr)
		numdays + 1
	/if

	firstDay = scalarFromYMD(yr, mo - 1, 1) + 1
	firstDay = int(firstDay) mod 7

	print
	for j in 0 .. 6
		echo daynames[j], ' '
	/for

	echo " |--- ", months[mo - 1], ", ", yr, "\n"

	` adjust starting day in table

	for day in 0 .. firstDay  echo "    "
		day = 0
		while day < numdays
			day + 1
			firstDay + 1
			firstDay = firstDay mod 7
			if (firstDay = 0) and (day <> 0) print
			if day < 10 echo ' '
			if (thisDay = day) and (thisMonth = mo) and (thisYear = yr)
				echo '[', day, ']'
			else
				echo ' ', day, ' '
			/if
		/while

		mo + 1
		print

	/for

return 0


main($argc, $argv)