TYPO3 date issue
Solution 1:
You need to use underscores in SQL, therefor the mapping is not working.
Extbase expects a SQL field named start_date when you use startDate in your model.
It's quite hidden in the Extbase Docs, but I found it (and will change it to be more prominent): https://docs.typo3.org/m/typo3/book-extbasefluid/main/en-us/6-Persistence/1-prepare-the-database.html#preparing-the-tables-of-the-domain-objects