In this case, Supreme Court was concerned with a Central Government Employee.
The Court was examining Rules of Central Civil Services (Pension) Rules, 1972
In this case Extra Ordinary leave was granted to avoid break in service. It was not considered as period spent on duty by court. UOI Vs A.K. Sharma 2011 (1) SCALE 700 on page 703 para 9
In other cases of Extra Ordinary leave with medical certificate, different consideration may arise.