Steps to reproduce:
1. Set date pattern to 'Y-M-D;M-D'
2. copy-paste a text date value from a text document into a cell, e.g. '2014-08-26'
3. press the 'format as date' button
Puts an ` character in front of the text, does not recognize it as a date. This means you can't paste dates into a spreadsheet and have them recognized / sorted with dates that you manually entered into the spreadshit
Should read the string and recognize it as a date.
Operating System: Ubuntu
Version: 18.104.22.168 release
While the technical details are beyond me this is well known (and happens on other office suites). That being said: http://extensions.libreoffice.org/extension-center/ct2n-convert-text-to-number-and-dates
I've already requested that this be added in core so I'm going to close this bug as a duplicate of mine. There are reasons to not implement it (again, the technical reasons are beyond me) but the request is out there.
*** This bug has been marked as a duplicate of bug 33962 ***
It would already help to check the option "Detect special numbers (such as dates)" when pasting such string from an external application. And for the ISO 8601 dates in the format YYYY-MM-DD you don't have to change the date acceptance patterns, they are always recognized.