Format of date to allow storing correctly in EXIF

What format should be used so the date is stored correctly in the metadata

Hello David. Are your dates misunderstood by the system (and the wrong date get stored) or the date is missing from the EXIF data?
Basically the software tries to interpret the date no matter the format. To make sure it's working properly, enter year, month and day numbers in a format like this:
yyyy-mm-dd or dd.mm.yyyy or mm/dd/yyyy

If you are not happy with the date recognition, please send me a few examples of dates you enter and describe what is the desired date. Maybe I need to improve the date recognition algorithm.