https://bugs.documentfoundation.org/show_bug.cgi?id=144359
--- Comment #7 from Mike Kaganski <mikekagan...@hotmail.com> --- (In reply to Edward Redondo from comment #6) > My typo "9/081/2021" typo in a date-formatted cell would have the "081" in > red telling me that is a wrong entry for the date format. Is that doable? No. 1. Format string does not limit the ways that you may *enter* the valid date. E.g., defining a date format like MM/DD/YY, you may enter "aug 1" (in a cell with en-US number format), and get it converted to a date; or you may enter "2021-09-09", and also get it converted. Or you may enter 10%, and the entry will get recognized. Or 1 2/3. And so on. All these will get recognized as a valid *number* (using different rules built into the program string parser), and will end up as valid numbers in the cell. 2. More importantly: each number format string may consist of *four* parts: for positive numbers; negative numbers; zero; and text. If you omit any part, it is *not* considered "absent", but a default value is implicitly used for the respective part. So your partial format string MM/DD/YYYY in reality is equal to something like "MM/DD/YYYY;MM/DD/YYYY;MM/DD/YYYY;@", where the last fourth part tells "show text as it was entered". So any text is *valid* from the format point of view. And there is no way to make it invalid. Any data *matches* any format string. And format string *has no idea* why the program decided that this cell is a text. But you may use custom format string like e.g. "MM/DD/YYYY;MM/DD/YYYY;MM/DD/YYYY;[red]@", which would mark red all texts, regardless of the reason why it is text. You may learn more about format strings in help: https://help.libreoffice.org/latest/en-US/text/shared/01/05020301.html?&DbPAR=CALC -- You are receiving this mail because: You are the assignee for the bug.