Invalid serialization data for DateTime object

Rather than saving the DateTime as a string, have you considered saving it as an integer, that is the number of seconds, as you are getting from time()?

That would remove the parsing problem and make it easier to transform the date into something easier to process. You can always turn a time() into a DateTime.

Yea, it could be a solution. But I prefer to solve the problem because I think is a Codeigniter problem.

Thank you.