Not sure if this exists already, but in many places like UNIX time is represented just like that anyway, and we have functions like unix2datetime in Dates to make interoperability work. However, you have to pass in an integer, not a float, currently. Maybe a wrapper type EpochDateTime or so would work where you can choose the reference time point and unit via type parameter. And convert over to DateTime lossily via round(DateTime, e::EpochDateTime) so it would be clear that this is not exact.