[Admin UI] Update date filter format to be datetime instead of date

[seanpreston]

Is your feature request related to a specific problem?

In order to merge #376 and solve the issue around single day date filtering, we need to be sure the frontend is only sending date filters in a datetime format. Currently they are sent only as dates.

Describe the solution you'd like

When the frontend makes the request, have the date filters sent in the format %Y-%m-%dT00:00:00.000Z