Hey!
Just to clarify:
The German translation of the timing is a bit tricky.
Those campaign emails are not sent on a date, but released on that date. It means the sending will be done starting from that date. If you join the campaign later, you will get those emails right away.
With segment emails you can specify a sending window. Make sure you are setting the END of the send as well:
Make sure you have your crons ready as well. You will need the mautic:broadcast:send cron to add the emails to the queue and mautic:emails:send will dispatch them from the queue. (If you use queue.)
Good luck!