I decided to check the source code using grep. Here is example using CTOD.
IF NOT EMPTY(ld_bdate)
lc_filt = lc_filt + ;
[ AND STR(trandte-CTOD("01/01/1901"), 8, 0) + ] + ;
[vendno + invno >= STR(ld_bdate-CTOD("01/01/1901"), 8, 0)]
ENDIF

I hope this helps.
John