PARM varname
# Create a name of form: "mmmdd" e.g. SEP27, where the day is for yesterday
# Handle case where yesterday is end of previous month.
if hpdate <> 1 then
   setvar !varname word(hpdatef,,2)+rht("0"+decimal(hpdate-1),2)
   return
endif
# deal with calculating last day of prior month
if hpdate = 1 and hpmonth = 3 and hpyyyy mod 4 = 0 then
   # deal with today being Mar 1 on a leap year
   setvar !varname "FEB29"
else
   # circularly shift month 'array' and day 'array' right by one entry
   setvar !varname &
       word("DEC,JAN,FEB,MAR,APR,MAY,JUN,JUL,AUG,SEP,OCT,NOV",',',hpmonth)+&
       word("31,31,28,31,30,31,30,31,31,30,31,30",',',hpmonth)
endif