SLA with Time and dates excluding weekends, holidays and multiple no-working hours

Hi, welcome to the forum.
I suggest you read up on the formula functions, you've got NETWORKDAYS that will do just that for you

I suggest adding a helper column that calculates the working hours.
Without a file I'm not going to try and imagine what your file and dat looks like.
The NETWORKDAYS shows the effective working days and if you use it correctly also skips the holiday dates, this will have to be a separate raneg of all the valid holidays for that period, you could even hav a list of all the holidays between the minimum data of your entries and set a maximum to a the current date + one year in taht way it covers everything at all times, the helper column next to thsi will also have to add the working hours and there you will have to account for the weekend, holiday and whatever exceptions, only then you will be able to also shoud the actual SLA hours.

You will have to play with it.
I added two rows with some test but this is much more complicated.
Like I said, you will have to include several helper columns between column B and Column C that actually calculates the effective date AND time.
Read your private message but I think you should keep it in the open forum.
I don't understand with 'I cannot add helper columns'
I've attached my minor modification
Maybe you should consider resorting to using a macro.

Read your private message but I think you should keep it in the open forum.

You MUST keep it in the open forum!

Forum Rule #8: Do not private message forum moderators or members for Excel help. (A, Z)

No this was just to show you how to use the newtworkdays AND the holiday dates
I still don't knwo WHY YOU cannot add helper columns,

Looking at your file and looking at the macro's I see you have a lot of exception hours and times.

Please specify ALL the exceptions and WHAT is it you really want me someone to help you with?

You have a START SLA date and the number of days it should be completed.
And I am ASSUMING but YOU must tell us that the day is always 24 hours and that you DO NOT count WEEKENDS but I also noticed tou include some time values 13 hours and all that

WHAT are the working hours you need to take into account? YOU have 44 columns of dat with values and formulas and the date format shows 12:00:00 PM with means midnight of that date so
the first SLA date 3/27/19 12:00 PM means it is the start of march 28.
WHY don't you sue the 24 hour format?
Well first answer as much as you can and maybe even attach a (manual) result of the contents of the columns A,B and C that you want to see.

See, it's a question of patience, I will look later today and see if I can advice you.
Trust yourself and you can do it

The Holaday dates I gave it a the range a name: Holiday_Dates
I inserted two extra helper columns that show TRUE if it's a Holiday and the other it it's a weekend
Maybe this helps you I did not really look at your helper columns because I don't understand what you're doing and don't have the time to really analyze it.