A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
With start date in A2 and end date in B2:
Years:
=DATEDIF(A2, B2, "y")
Months:
=DATEDIF(A2, B2, "ym")
Days:
=B2-EDATE(A2, DATEDIF(A2, B2, "m"))
(Remark: DATEDIF(A2, B2, "md") is not 100% accurate)
Format the cells with these formulas as General.