CohortMembership start and end: datetime or just date?

In the work on TRUNK-4906 we have expanded cohort membership to include a startDate and endDate.

I just noticed that while the fields are startDate and endDate, they are actually datetimes in the database (not just dates) and the code generally treats them as date+times.

I don’t think we ever explicitly discussed this in our design calls, so my question is: what would be the desired behavior? Is there a use case for being able to say that someone was enrolled in a cohort at 2017-04-26 09:15:00? Or do we want to limit things so you can only say enrolled 2017-04-26?

Fine with me to change them have no time component.

@darius what are the disadvantage of having datetime instead of date?

We discussed on today’s design forum and decided to use timestamps for start & end dates. Apps can ignore times if they want, but this will allow apps that need more granular memberships (e.g. hourly) to still use the API.