Incorrect data type for operator or @function:Time/Date expected

The user gets an Meeting invite and when he try to open it this error shows:

Incorrect data type for operator or @function:Time/Date expected

I try to copy the message over to my mailbox, same error in my mailbox

Help???

Subject: Incorrect data type for operator or @function:Time/Date expected

Check the date field in which you might be storing a string which needs to be converted to a dateTime value.