Error message

• Warning: date_timezone_set() expects parameter 1 to be DateTime, boolean given in format_date() (line 1938 of /opt/web_data/www/crystals/includes/common.inc).
• Warning: date_format() expects parameter 1 to be DateTime, boolean given in format_date() (line 1948 of /opt/web_data/www/crystals/includes/common.inc).