lNot a direct function like EOMonth but
=Date(Year(A1),Month(A1)+1,) works
When you leave off the day from the inputs Excel picks the last day of the
prior month, so when you use Month(A1)+1 you get the last day of the current
month.
Even works for leap years 2/15/2004 in A1 yields 2/29/2004.
Kind of an odd quirk, like it is picking the 0th day of the month. Not sure
if this was intentional on the programmers part, but it works.