Excel one cell formula for calculating Actual SLA End date & time

JoeUser2004  i think Bob_m_m wanted a formula to calculate the END time not how much time is in between 2 values.  Here is my formula (that works on older excel):

=IF(E6+6/24<=INT(E6)+$D$3,MAX(E6,INT(E6)+$E$3)+6/24,$E$3+1+6/24-$D$3+MIN(E6,INT(E6)+$D$3))

 and using the newer LET:

=LET(in,E6, delay,6/24, dEnd,$D$3, dStart,$E$3,
d,INT(in), h,in-d, freeze,1-dEnd+dStart,
IF(h+delay<=dEnd,MAX(in,d+dStart)+delay, freeze+delay+MIN(in,d+dEnd)))

this version is a little easier if you need to tweak values and hopefully a little easier to understand/see what is being done.