Topic: Fatal error: Cannot redeclare date_diff() in /home/Fatal error../inclu

Fatal error: Cannot redeclare date_diff() in /home/........./includes/functions.php on line 191

I know nothing about DeltaScripts etc. as This website was developed an then hosted before I came on board with the company who owns this website.  The above is the message received when we try and access the website.  I have no idea how to fix this.
Any advice would be appreciated.
Thanks
Brad

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