Update items by day

Hello,

I have a feed that imports items every 1 hour.
As it creates a large amount of items (24 by day) I would like to keep only the last item every day.
The best way is to create a date only field and to mark it as unique, so that the feed should update one item every hour and create a new one the next day.

Is there any way to do that ?

PS:
I tried to use tamper to set the date only field (format Y-M-D) from Timestamp to date but the website hangs with this error:

Drupal\tamper\Exception\TamperException : Input should be numeric. dans Drupal\tamper\Plugin\Tamper\TimeToDate->tamper() (ligne 62 de /web/modules/contrib/tamper/src/Plugin/Tamper/TimeToDate.php).

Thanks