I'm not sure I agree. When I convert fields to DateTime, I remove the unit suffix from the name. The DateTime is supposed to be an implementation-agnostic point in time. It shouldn't come with any units, and nor should they be exposed by the internal implementation.

The factory method used to convert e.g. Unix timestamps to DateTimes, now that should indicate whether we're talking seconds or milliseconds since epoch, for example, and when the epoch really was.