dates in excel wont format correct

There are some funky logical problems with date number formats.

Say for example your computers default date format is dd/mm/yyyy, you use the "Date" number formatting. Someone say for example an american opens with mm/dd/yyyy it'll be fine. The "Date" number format converts the serial number correctly. 

If you use custom, say for example "dd-mm-yyyy", it will force that format. Dates like 12/12/2019 are super awkward with these "custom" formats. You must follow the custom formatting rule, it will not intelligently convert.

Your date format "yyyymmdd" might also not auto apply the date serial.

For example, type in 20190719 to a cell with that format it'll #### because it's assuming that number is the date serial, trying to convert that makes it too large. Even in a custom date format, you type in your normal date format (for example dd/mm/yyyy or mm/dd/yyyy).

It's best practice to have an "Input" in these intelligent formats, and an output in your custom. If thats possible that it.

If you've got data in that yyyymmdd you need to convert back, use "=Date" in a similar way.
"=DATE(MID(A1,1,4),MID(A1,5,2),MID(A1,7,2))"

kgoldie