BoniM wrote...
....
Just one teeny thing with your formula, tho... If the start
date/time is 1 pm, your formula returns 9 the next morning,
instead of 5 pm.
....

If the 4 hours later in B2 is the END of the period begun in A2, I'd
agree, but there's a simpler approach.

=A2+IF(MOD(A2,1)-"13:00:01"<0,1/6,IF(WEEKDAY(A2,2)=5,2,0)+5/6)

If B2 is the beginning of the next period after the period beginning
in A2, I'll stick with 13:00 - 09:00 next workday.