Timestamps in magic aren't always right

[rbubley]

After updating a property name, and resyncing with magic from the CLI, I got the usual style of message:
Are you sure you want to sync "XXXXX" with X model(s) that was modified on 2016-12-07 at 16:09? (Y/n): Y

But this timestamp was the last time I had updated the model more generally, and didn't reflect the time I had renamed the property.