the hours of operation of two device

Solution for all Excel users with a help table:

Please try in J1: 00:00:30 and in J2 =J1+1/1440 copy down until J1440.

Please try in K1 and copy down:

Formula:

=IFNA(J1>INDEX($B$4:$B$13,MATCH(J1,$A$4:$A$13,1)),TRUE)*IFNA(J1>INDEX($E$4:$E$13,MATCH(J1,$D$4:$D$13,1)),TRUE)

Solution:

Formula:

=SUM(K1:K1440)/1440