Maybe you have to give a clearer set of rules about what is a valid input.
Is it now only
date in format mm/dd/yy (leading zeros optional)
time in format hh:mm:ss ( 24H clock, leading zeros optional)
floating point xxxx.yyyyy ( maximum number of Xs = ? , maximum number of Ys = ?, cannot start with just a '.', must convert to a 4 byte float?)
Ruled out :
exponential formats, currency symbols, etc. etc. ?