Average of ending time in a columns

If the times are just times and there is no date element
as an array with shift ctrl enter

=MOD(AVERAGE(IF(A1:A7<0.5,A1:A7+1,A1:A7)),1)

so if the shift finishes in the first half of the day <0.5 I assume it goes over midnight

If the average finish time is after midnight the value will be for example 1.00034 so the mod function, changes this to 0.00034

think that's all!