FileMaker 12 includes an undocumented Get ( UTCmSecs ) feature, which can be used for timezone-independent timestamps with millisecond precision: GetAsTimestamp ( Get ( UTCmSecs ) / 1000 ) = Greenwich mean time to 3 decimal places. This is great for sub-second timing and for determining the timezone of client and host devices, as the GetUTCOffset custom function illustrates. This is a great feature to have; but, as many developers have noted, it isn't supported and there's an above-average chance that it wont exist in future versions. I don't like either of those things. This is functionality worth having, so lets ask for it!
Here's FileMaker's feature request page: http://www.filemaker.com/company/contact/feature_request.html
I realize that "Get ( UTCmSecs )" is unusual for a FileMaker native function, so I've requested an equivalent "Get ( CurrentUTCTimestamp )" function, which would return the same result as GetAsTimestamp ( Get ( UTCmSecs ) / 1000 ).