Hai,
There is a lot wrong with the datetime input in SMW.
1: in order for a datetimepicker to work, a datepicker _must_ first be called. We solve that by using an invisible div: https://wiki.sha2017.org/index.php?title=Form:Lightning/Event&action=edit
2: in this form, and others, the first selected value of the datetimepicker (when creating a new thing) is never saved. It is only saved after editing the existing value. Bulk adding is impossible in this way.
You can try here:
https://wiki.sha2017.org/index.php?title=Form:Lightning/Event&action=edit
Regards,
Elger / Stitch