Error message

• Warning: date_timezone_set() expects parameter 1 to be DateTime, boolean given in format_date() (line 2062 of D:\home\site\wwwroot\includes\common.inc).
• Warning: date_format() expects parameter 1 to be DateTimeInterface, boolean given in format_date() (line 2072 of D:\home\site\wwwroot\includes\common.inc).