Graph with time based horizontal axis - Excel 2016

May need to see an actual sample of the data, because Excel should be able to treat the dates properly in either scatter or line chart types. A scatter chart's x axis should be readily formatted as date (using number format), so I am not sure why you could not format your scatter plot to show dates. A line chart that fails to recognize a date axis (automatically or when manually forced) is somehow not recognizing your dates as dates.

If I were to look at your spreadsheet, the first thing I would probably check is to see if your "dates" are true date/time serial numbers or if they are text strings that look like dates (probably test with the ISTEXT() function). Numbers/dates stored as text is a common source of these kind of issues.

The dates are formatted as dates as per the format cell option / date.

It can be important to recognize that number formatting cannot change the underlying value. If a cell contains a "number/date stored as text", changing the number formatting does not change the text value.

I don't know what error checking options you have turned on in your copy of Excel (I have most of them turned on). Upon opening your sample file, I noticed little green error triangles on some of the dates in column A. The indicated error is "text date with 2 digit year". I could use the dropdown on each error cell to convert to an actual date value/serial number, but that would get tedious to do them all individually. I tried using the Text to columns approach, and that worked for the few samples given, and the chart immediately reverted to a date axis. I recommend reviewing this help file to review the available strategies for converting numbers/dates stored as text to numbers: https://support.office.com/en-us/art...1-c5bad0f0a885 (note that change number format on cell is not an option).

From there, you may need to try a few things to see how things like your local/regional date/time setting impact how Excel recognizes and converts dates stored as text and make sure that you get a solid strategy in place that will correctly convert all of the dates stored as text to appropriate date serial numbers. Once you have that in place, your chart should revert to a date axis automatically.