“The time of sunset is defined in astronomy as the moment when the trailing edge of the Sun’s disk disappears below the horizon.” This is how Wikipedia defines sunset, so this is the only time of sunset, and any later time when sun rays disappear from horizon, is end of Dusk, but not sunset as explained by wikipedia:- “Sunset is distinct from dusk, which is the time at which the sky becomes completely dark,”
So long as it is on different days (as opposed to the same day) is akin to Availus in Omer, that 1 year one can observe 1st 33 days, and next year observe last 33 days, or vice versea, all this so long as it is on a different year.