The plugin is better for clarity, but adds a delay of a round trip to another server.
The workaround is better for speed, but the hacking together of various functions makes it harder to see what is going on.
The workaround is an expression of:
Current date/time
zero out seconds
add seconds: PMT (rate 0 nper 1000 pv Current date/time, zero out seconds, extract milliseconds )
add seconds: date_in_seconds_to_convert
I hope that makes you laugh : )