When I open a excel file that has date strings like 2017-11-02 and time like 11:45:35, LO opens them with data format 2/11/17 and 1/1/04. Why does it not automatically recognize them as valid dates and times, and is there anything I can do to fix that?
These are valid dates, just represented in a different date format (i.e. 2/11/17 is the same as 2017-11-02, but formatted as D/MM/YY instead of YYYY-MM-DD). You’ll also see if you position the cell cursor on such cell and look at the Input Line on the top bar. There are various reasons why this could happen, a reasonable assumption is that the Excel format uses a system custom format, which is not or not fully implemented. Without seeing the actual format code string of such cell there’s not much that can be said.