Not possible to clear "deadline_registration" in backend once it was set

[mk-mxp]

When adding a seminar via backend, it is possible to not set deadline_registration. Then it is OK to leave it empty on further editing that seminar. Once a deadline_registration was set, it is no more possible to remove it (set to empty). It may be related to Typo3 9.5 not allowing to enter "0" for a date, but having a clear icon wiping out the value.

The problem comes up before the TCE value hook is triggered, which then is provided with the old seminar data (with the old deadline_registration value set).

[oliverklee]

Are you using MySQL in strict mode? (This might be a bug in the TYPO3 core.)

[oliverklee]

And could you also please test (without any changes to your MySQL configuration) whether it helps to change the eval for the deadline_registration field in the TCA from datetime to datetime,int?

[mk-mxp]

It is a MariaDB 10.4.12, modes are:

MariaDB [(none)]> SELECT @@GLOBAL.sql_mode;
STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

Setting eval to your suggestion does the trick.

[oliverklee]

I have reported a bug for the Core: https://forge.typo3.org/issues/91731