Yes interesting addition to the API. From my observations it appears that it is actually UtcTicks rather than (say) the Unix Epoch Timestamp.
The docs indicate that The value of the UtcTicks property represents the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight on January 1, 0001
For me (in php) I use the Unix Epoch Timestamp. Python I believe also uses the January 1st, 1970 at UTC as day 1.
Just an FYI the conversion of UtcTicks to Unix TimeStamp would be: TimeStamp = (UtcTicks - 621355968000000000) / 10000000
Hopefully @lubos will confirm it is “UtcTicks” being represented.