How BSON decodes a datetime

gistfile1.py

def _get_date(data, position, as_class, tz_aware, uuid_subtype):
    millis = struct.unpack("<q", data[position:position + 8])[0]
    diff = millis % 1000
    seconds = (millis - diff) / 1000
    position += 8
    if tz_aware:
        dt = EPOCH_AWARE + datetime.timedelta(seconds=seconds)
    else:
        dt = EPOCH_NAIVE + datetime.timedelta(seconds=seconds)
    return dt.replace(microsecond=diff * 1000), position