Time Calculation

[Don Meredith]

We make parts that are subjected to a heating process that affects flatness and parallelism. This distortion relaxes at a known rate over time and has a tolerance allowance for how long since the parts were heated.
Currently, the operator enters a time frame via Comment/Input ("A"- up to 8 hours, "B"- 8-24 hours, "C"- more than 24 hours).
I'm looking for a way to have the operator enter the time from the Lot Summary Card and have the software compare it to the System Time to determine which Tolerance to apply.
From what I've been able to learn so far, I need to find a way to convert System Time and the time entered by the operator to Epoch Time, then compute the time difference.
Any ideas?

[Douglas]

you will need your guy to enter heating time in ISO 8601 time format, other than that assign system time to a variable and a straight subtraction works I believe

[Don Meredith]

Thanks, Douglas. Getting the operators to enter anything besides straight time in AM/PM format won't fly. Also, I tried the subtraction approach and it didn't work for me. I need a way to convert date/time to a numeric string. I'm thinking maybe a VB script (about which I know nothing) in a Subroutine.

[Douglas]

the one for time at which the program is run should be this simple I think... if you do not need the date involved

ASSIGN/TIME=SYSTEMTIME("HH':'mm':'ss")

[Don Meredith]

Assigning System Date and Time and Heat Event Date and Time is not the problem - I got that part. What I need is some kind of code to calculate the difference.