Error message

• Warning: date_timezone_set() expects parameter 1 to be DateTime, boolean given in format_date() (line 2062 of /var/www/tl-multi/www/includes/common.inc).
• Warning: date_format() expects parameter 1 to be DateTimeInterface, boolean given in format_date() (line 2072 of /var/www/tl-multi/www/includes/common.inc).