When comparing a date without time to a date with time they should be considered equal if the date part is the same

[Nicklas Nordborg]

This may happen if, for example, time information is missing from Sampling date+time or RNA later date+time.

[Nicklas Nordborg]

In 6976:

Fixes #1443: When comparing a date without time to a date with time they should be considered equal if the date part is the same

Timestamp values are now compared also at midnight.