We have a situation where our SharePoint 2013 site's regional settings are Finnish. That means the date format is dd.mm.yyyy. We created a document set content type with a datetime column.
The datepicker in that field works as It should and the date given by it is in a correct format. But when we pick a date 25.1.2013 (25th of january) we have an error when saving the document set: "String was not recognized as a valid DateTime." If we change the date to 9.1.2013 (9th january) the save will succeed, but displaying the properties shows us the date was saved as 1.9.2013 (1st of september).
This only happens when creating a new Document Set. If we edit it and save, the date field works like it should. Also this doesn't happen in custom lists or document content types. Only Document Sets. The document set content type was created manually trought site administration, no visual studio or xml was used. This happens on an On-Premise server and on the SharePoint Online Preview.
We've tried settings users locale from user profile, but no luck.
Is this a bug or is there something we don't see?