In the following example, as you can see in the photo, a fraction of the year can be identified by the YEARFRAC function.

=YEARFRAC("9/18/2022","12/29/2022",0) ----->>>>answer is 0.28
=YEARFRAC("9/19/2022","11/24/2022",1) ----->>>>answer is 0.18
=YEARFRAC("9/20/2022",'10/25/2022",2) ----->>>>answer is 0.097
=YEARFRAC("9/21/2022","12/26/2022",3) ----->>>>answer is 0.26
=YEARFRAC("8/22/2022","9/27/2022',4) ----->>>>answer is 0.13
YEARFRAC Function
The YEARFRAC function is one of the Date & Time functions of Excel.
It Returns the year fraction representing the number of whole days between start_date and end date.
YEARFRAC arguments
1. End date section is a serial date number that represents the start date.
2. Start date section is a serial date number that represents the end date.
3. Basis section is the type of day count basis to use.