Find the day of the week

Part of the thread in 3000-L on leap years touched on obtaining calendars for dates in the future. Steve Barrett contributed the following:

"Here's a command file that returns the day of the week for a given date. Nothing fancy -- no syntax or reasonableness checks."

parm d="01/01/2000"
setvar cal_day "!d"
setvar mo str(cal_day,1,2)
setvar day str(cal_day,4,2)
setvar year str(cal_day,7,(len(cal_day) - 6))
setvar wkday "SUNMONTUEWEDTHUFRISAT"
setvar wdleapy "034025036146"
setvar wdleapn "144025036146"
setvar century !year/100*100
setvar yr !year-!century
setvar wday wdleapn
if (((!year mod 4) = 0) and ((!year mod 100) <> 0)) or ((!year
mod 400) = 0)
   setvar wday wdleapy
endif
setvar dv str(wday,!mo,1)
setvar dayval (!yr/4)+!yr+!dv+!day
if (!century mod 400) = 0
   setvar dayval (!dayval - 1)
endif
setvar dayval (!dayval mod 7)
if !dayval = 0
   setvar dayval 7
endif
setvar daywk str(wkday,(!dayval*3-2),3)
echo The day of the week for !cal_day is !daywk.

Find the day of the week

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