There doesn't seem to be a way to get calc to set the date format default to 4 digits for the year, at least none I could find documented. I suspect I am not alone in wanting that feature.
This isn't so much a bug report as a feature request but I couldn;t find where else to suggest it. Would it be made possible to set a default date format in calc? Personally I would really like the 4 digit year to be my default. Other people may have their own prferences.
You can use menu Format-Cells, Numbers tab. Select Date category and in Format list you'll can select from many variant include 4 digits for year About documentation: just read a Calc guide https://wiki.documentfoundation.org/Documentation/Publications#LibreOffice_Calc_Guide Status => NOTABUG