fatal error date_field_get_sql_handler()

hey, i have since two weeks a fatal error report:
Fatal error: Call to undefined function date_field_get_sql_handler() in /home/.sites/94/site2485/web/sites/all/modules/signup/includes/date.inc on line 302

i already searched in the internet for it but i couldn't solve the problem.

i'm a windows user and so i don't know how to usw the patch. please tell me what to change in the php, thats much easier for me.

moreover i found in the protocol the error report that the a guest tries to start a cronjob but cron is already working. i found this errorreport about 10times a minute-

i hope that somebody can help me with me problem.