How to calculate (cell reference - DD/MM/YYYY) inside formula?

The DATE function will work in the DATEDIF function but you need to get your () and " right.

If the start date is in A2, then you can do this:

=DATEDIF(A2,DATE(2023,7,17),"M")

Use ; instead of , in the formula if your region uses , as the decimal separator.

SG

Use Badunit's answer, but read up on DATE function

DATE - Apple Support

It always takes Year, month and Day as arguments, thus it doesn't matter your computer regional date settings, it will always work.

It also allows you to use some tricks like finding the last day of a month by using the next month and 0 for the day portion.

=date(2023,3,0) will give you last day of February.

Jason

Basilisk2, a few pointers to reduce your frustration.

1- The only way Numbers converts 17/7/2023 into 17÷7÷2023 as you said first, is because you typed =17/7/2023 in the cell. It's a simple value, do not use =.

2- Are you sure Numbers expects you to enter dates in the DD/MM/YYYY format? In my locale I have to use YYYY/MM/DD. You can check the expected format in File / Advanced / Language and region. If you enter the date components in an order that doesn't make sense for your local format, Numbers is not going to understand that 2023 is a year and not a day. By entering components in the correct order you can actually skip the century, thus 23 is automatically converted to 2023 and shown accordingly with the proper date format. / and - can both be used as separator.

3- To embed a function into another one, you can just select it when you're highlighting the appropriate argument of the first one.

First insert function DATEDIF from the function selector in the panel (if you don't see it click on Format in the toolbar).

Then when end-date is highlighted (dark grey), insert function DATE from the panel, and boom, all parentheses place themselves correctly.

Best method is to use the DATE function to create the one date.

DATE(2023,7,17)

You can put quotes around a date like "17/7/2023" but that is kind of iffy. Your "5/1/2023" and my "5/1/2023" are not the same date.