Should not build the date separator depending on client Timezone

Timestamp of all photos is assumed to be in America/Los_Angeles Timezone. This creates problem when this timestamp is interpreted in the client in a different timezone. The client assumes the timestamp is in its own timezone...

Anyway, all users in any timezone should see the same date for a given photo, so no timestamp should be interpreted (e.g. phpjs.date(ts) or new Date(ts)) in the client.

This is independant from the fact that the photo has or not a timezone information.

Not sure if this is explanatory enough. I can explain/give use case/test photos if needed.

This bugfix is kind of hacky. You might want to rewrite everything in UTC as per https://github.com/photo/frontend/issues/321