/*
	dtadd:

	Determine the future date given current date and the number of
	years, weeks, or days until yymmdd.
*/

program define dtadd
version 2.1
	if "%_*" == "" {
		di in red "invalid syntax -- see help dtadd"
		exit 198
	}
	if substr("%_3",1,1)=="d" { mac def _3 "d" }
	else if substr("%_3",1,1)!="y" { dtadd }
	if _N != 0 { 
		di in red "no; data in memory would be lost"
		exit 4
	}
	quietly set obs 1
	gen double DATE1=%_1
	ftoe DATE1, gen(JDATE1)
	gen long NDATE2=JDATE1+  %_2 * cond("%_3" == "d", 1, 365.25)
	etof NDATE2, gen(FDATE2)
*
* Assumes both days of the dates shown are worked
*
	di _n %7.0f "Future Date is:   " = FDATE2
	drop _all
end