Improve handling of invalid dates

[mpostelnicu]

There are several invalid date issues in the database. The default behavior of DateTime::createFromFormat PHP function is to print warnings for invalid dates as long as the string is still parseable.

If warnings are detected, it is better to fail and print the error. This will catch invalid dates such as 0000-00-00 which are correct dates in terms of format, but are not "real" dates