Hang on, i just found this Calculate days between two dates
But i don't know how to convert the date format into 10/05/18
Oh and it's also confusing because here in the UK we use day/month/year not month/day/year 
okay so step 1: Julian Date?
I could use the JD function (Julian Date) to convert 19 Jan. 2024.
So would that be JD(19 Jan. 2024)?
Oh shoot I can't do that because it has to be in this format:
JD( year, month, day )
so it would need to be JD(2024, 01, 19) presumably
Hmm. I suppose I could use RegEx to do this
update -- today is simply JD()
So that gives the right answer! That is super encouraging!