Datasource grouped by datetime outputs old entries

[mprofitlich]

The setting:

• Datasource is grouped by datetime
• Datasource is filtered to show entries only that are equal to or later than today

The datasource outputs old entries if an entry comprises multiple timelines of which at least one is today or later. The expected behaviour would be to output only entries that have a timeline that fits the filter.

This issue might be connected to issue #189