What's an example of a date string that the datepicker can't read?

2020/12/08

I can't reproduce that problem - for me, the "datepicker" input picks up the string "2020/12/08" fine (and then saves it as "2020-12-08"). What does the full field tag look like for that input?

I fetched and checked-out the latest from git on Dec 11, 2020 [1] and all our issues are resolved. Whatever you've done lately seems to have solved the issues. Legacy date formats are being handled by datepicker and the save button JS errors are gone. Thank you!

We don't have to debug this further for my part, but I see that there are a few recent commits relating to datepicker and page saving with hidden mandatory fields. Can you confirm if you have found and resolved some issues that are likely related to what I reported?

[1] https://github.com/wikimedia/mediawiki-extensions-PageForms/commit/75103fb454b5141dc14eb27e0a656028af4600ce