sorry for the last minute feedback, but i wonder if we should protect against this, either in this function or in the calling function:
```
>>> sorted([None, datetime.now()])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can't compare datetime.datetime to NoneType
```

it looks like the current behavior would be that if any action didn't have a server date (which is possibly a legacy property that wasn't always set back in the day) you could never submit against that case again. 

alternatively we could convince ourselves that never happens by inspecting the existing data, or fix the 500s if they start coming in (not necessarily my favorite plan).