Unable to create DateTime object

Hi,

When I try [smallcalendar https://calendrier.charentonvolley.fr/smn1%5D
I’ve got this error message :
Message displayed to logged in admin only:

Unable to create DateTime object from jeu. 01 janv. 1970 00:00:00 UTC
DateTime::__construct(): Failed to parse time string (jeu. 01 janv. 1970 00:00:00 UTC) at position 0 (j): The timezone could not be found in the database
!
Impossible de charger ou de mettre en cache le calendrier iCal https://calendrier.charentonvolley.fr/smn1