Reading the documentation, I don't understand how this is not possible : 

# get the max utc timestamp
ts = datetime.max.replace(tzinfo=timezone.utc).timestamp()

# similarly 
ts2 = datetime(9999, 12, 31, 23, 59, 59, 999999, tzinfo=timezone.utc).timestamp()

# timestamp value 253402300800 seems correct
# converting back to timestamp is impossible, these all fail : 

dt = datetime.fromtimestamp(ts, tz=timezone.utc)
dt = datetime.utcfromtimestamp(ts)

It should be possible to get a datetime back from the initially converted timestamp, no?