Opposite of `Timestamp.to_seconds`

[amadanmath]

Timestamp.to_seconds is there to convert the timestamp into seconds. It might be helpful if there was also the opposite method, to build a timestamp from seconds — for example, when you need to do some artihmetic on timestamps, like shift the timings. Maybe something like

@classmethod
def from_seconds(cls, secs):
    hours, secs = divmod(secs, 3600)
    mins, secs = divmod(secs, 60)
    secs, msecs = divmod(secs, 1)
    return cls(hours, mins, secs, msecs)

EDIT: Also, is there a reason why milliseconds are left out of to_seconds? timedelta.total_seconds returns sub-second precision. It is easy enough to round when one needs integral seconds.