so, I think what was actually happening is that due to DateTimeProperty's broken [un]serialization when it comes to timezones, https://github.com/benoitc/couchdbkit/blob/master/couchdbkit/schema/properties.py#L314 , this was getting stored like

`2013-07-15T15:33:49+07Z`

which gets loaded as

`2013-07-15T15:33:49Z`

which if it gets saved will lose that information, like on https://cloudant.com/futon/document.html?commcarehq%2Fcommcarehq/3c333911-f0ae-4b54-b67b-a621115b25a4 where we have

`modified_on: "2013-07-15T15:33:49Z"`

but the original case block was `date_modified="2013-07-15T15:33:49.270+07"`

So, the only way to migrate would be re-inspecting the case updates and converting to utc before storing these properties.  That seems like it would be involved, so not going to do that unless someone tells me to.

In any case, it might be nice to make our own DateTimeProperty that handles timezones so we don't have to throw away that information to get it in couch.