Here in Australia I share your pain
You need to be independent of the locality setting.
Set Field [ table::field ; Date ( month ; day ; year ) & Time ( hours ; minutes ; seconds ) ]
In your script, create a If that checks what version of FileMaker that is running the script and set the Variable depending differently if it is FMP or FMS
I had a compounded issue with another thing, but pushing the values into the Date, Time, and then TimeStamp functions has got me sorted now. Cheers