INT 21,2B - Set Date

	AH = 2B
	CX = year (1980-2099)
	DH = month (1-12)
	DL = day (1-31)


	on return:
	AL = 00 if date change successful
	   = FF if invalid date


	- sets DOS maintained clock
	- DOS versions 3.3+ also update the CMOS date where applicable