Add X days to a Received Date but Exclude Weekends/Holidays from a Date Table - db2

Question

I hope someone can help with a calculation that I am having trouble developing.
I am developing a report in a DB2 database that I need to add "X" number of days to a "RECEIVED" date/time when an order comes in between X and Y; but exclude Weekends and Holidays to add to the received date. I have created a [TBLCALENDAR] that lists the Weekends and Holidays (Example below); and from this, I want to ADD X number of days to a "DUEDATE"
tblCalendar]
DATE DAYOFWK DAY HOLIDAY
1/19/2019 7 Saturday
1/20/2019 1 Sunday
1/21/2019 2 Monday YES
So, for example 1, if I have an order that is placed on 1/18/2019 at 4:01pm; the due date should be 1/23/2019 at 11:00am.
Example 2: if I have an order that is placed on 1/18/2019 at
Conditions are:
Previous Date 4:01pm to Current Date 11:00am = Due Date should be + "X" business days by 11:00am
If order received Current day by 4:00pm = Due Date should be + "X" business days by 4:00pm
I have tried to reference the tblCalendar to get the [Received] date/time and add X number of days based off of an order, but it's not functioning the way I have hoped.
I have used the following code...but it doesn't exclude Weekends or Holidays when adding the specified number of days or have my order time requirement to take into account previous day after 4:00pm to current date of 11:00am:
RECEIVEDDATETIME + 2 days as DUEDATE;
I have also used the below code to reference TBLCALENDAR to find the # of holidays and weekend days in a date range:
( SELECT COUNT (*) FROM TBLCALENDAR AS C WHERE C.HOLIDAY = 'YES'
AND C.DATE BETWEEN TBLORDERS.RECEIVEDDATETIME
AND TBLORDERS.DUEDATETIME) +
(SELECT COUNT (*) FROM TBLCALENDAR
WHERE DAYOFWK IN (1,7)
AND DATE BETWEEN TBLORDERS.RECEIVEDDATETIME
AND TBLORDERS.UPLOADTIME) AS NONWORKINGDAYS
Expected field output
If order was received between 1/17/2019 4:01pm to 1/18/2019 10:59am = 1/23/2019 11:00am
If order received Current day by 4:00pm 1/18/2019 3:59am= 1/23/2019 by 4:00pm.
RECEIVEDDATETIME DUEDATE
1/17/2019 4:01pm 1/23/2019 11:00am
1/18/2019 10:00am 1/23/2019 4:00pm

Answer 1

Here is a solution without the time logic.
with tblCalendar(DATE, DAYOFWK, DAY, HOLIDAY) as (values
(date('2019-01-19'), 7, 'Saturday', '')
, (date('2019-01-20'), 1, 'Sunday', '')
, (date('2019-01-21'), 2, 'Monday', 'YES')
, (date('2019-01-22'), 3, 'Tuesday', '')
, (date('2019-01-23'), 4, 'Wednesday', 'YES')
, (date('2019-01-24'), 5, 'Thursday', '')
, (date('2019-01-25'), 6, 'Friday', '')
, (date('2019-01-26'), 7, 'Saturday', '')
)
, mytab (RECEIVEDDATE, DAYS2ADD) as (values
(date('2019-01-19'), 2)
, (date('2019-01-20'), 2)
, (date('2019-01-21'), 2)
, (date('2019-01-22'), 2)
)
select m.*, t.date as DUEDATE
--, dayofweek(date) as DAYOFWK, dayname(date) as DAY
from mytab m
, table
(
select date
from table
(
select
date
, sum(case when HOLIDAY='YES' or dayofweek(date) in (7,1) then 0 else 1 end) over (order by date) as dn_
from tblCalendar t
where t.date > m.RECEIVEDDATE
)
where dn_ = m.DAYS2ADD
fetch first 1 row only
) t;
The idea is to enumerate each day of the calendar after the RECEIVEDDATE (1-st parameter) starting from 1 with the following logic: the number of each day increases by 1 if it's non-holiday non-weekend day (the sum(...) over(...) expression).
Finally, we select a date with the corresponding number of days needed to add (2-nd parameter).

Answer 2

Solution idea:
Your tblCalendar is a good idea but I recommend to add the working day information instead of (only) flagging the holidays and weekends. The problem with the "off days" are that after you have figured out how many of them are in the period from your receive date to the receive date + X days you cannot easily add them because there could be other "off dates" in that perios again.
By numbering all the work days you could identify the workday which is closest (equal or bigger) to the receive date. Retrieve its number and add the X days to that number. Retrieve the date that has this work day number and you are fine.
The time logic should be built before that all because it could add another day to the X days.