Downloaded At column in Dataset history can appear off by one day

[jcpitre]

This is a minor issue but it can lead to some confusion.
The Downloaded At date is displayed in the browser's timezone.
The daily download currently starts at midnight UTC.
So for a download occurring at, say, 00:45 on sept 29th, it will show as downloaded the 28th to browsers located west of UTC.

I suggest to use UTC for that particular field, and put it in the header (e.g. Downloaded At (UTC))

I deemed this minor because it will probably be a problem only for MobilityData's devs.

[jcpitre]

Oh, and as long as we're on to minor stuff, since it's a date and not a time, the header could be Downloaded On (UTC)
I think the at is for a time (I'll be there at noon), vs on for a date (I'll be there on October 25)