You may need to upgrade the firmware in the 450 to get its PRINT/EMAIL instructions to support the _date:us _time:12. Does anybody know if the latest 450 PRINT supports those PRINT date/time commands?
The 450 did not originally support the _date:us _time:12 commands in their PRINT-type instructions, but I do not know if they ever added support for those PRINT sub-commands to the 450.
You could just format them manually, but you will get leading zeros, I believe. Use the :BCD format modifier on your command (date/time values are in BCD, but print V locations defaults to binary/decimal format), i.e.
"Power on at: " V1612:BCD ":" V1613:BCD
but it won't look as good as
_date:us "and" _time:12