Enable playback for date only series

Thanks for the awesome lib. I believe the following use case would be a valuable addition for the playback feature:

Given a dataset including a date only series (=without times), choosing the date column as a filter should enable the playback feature so that the useless timestamp `00:00:00`, which has to be added to enable playback, can be omitted.

This is particularly relevant if the dataset is fairly big (+2.5 million records) as the file size can be reduced dramatically.