Count number of Years, but not in sequence

I need to count the number of years a person worked.   For example in this range of dates, the correct count is 5.   What would be the formula?

1/1/1975

3/1/1975

4/1/1976

5/1/1976

2/25/2011

12/15/2013

12/31/2013

6/17/2022

7/31/2022

9/17/2022

TIA

Mike