How to Calculate End-Date for a given Startdate in business hours without holidays

Question

Hello Experts,
I need to create a plsql function where we need to determine end date for a task. For this, input will be only start date & number of hours allocated for that task. Based on this input we need to exclude Business hours & need to include only Business hours. and in the end we need to achieve the end date after the hour addition to the start date.
Example : INPUT: 03-OCT-2013 12:00:00 PM /
                              Hours Allocated 30 Hrs.
Business Hours - 11 AM to 9 PM.
So time starts from or Startdate is Friday 03-OCT-2013 12:00:00 PM. 
So If I want to calculate the end-date by adding 30 hours to it, it should come WednesDay 09-OCT-2013 12:00:00 PM because I excluded Weekends & considered only business hours that is 11 am to 9 pm.
I am not able to get any such guidance in Internet as most of the docs are having start & end date as input.
Please help!
Thanks in advance !!

Answer 1

Hi,
As Christ said, there's no nuilt-in Oracle function to tell whether a given DATE is a holiday or not, partially because there's so much local variation in holidays.  You can write a function like that (see http://forums.oracle.com/forums/message.jspa?messageID=3351081 ), but creating a table will be simpler and more efficient.
I suggest creating a row for every date, whether it's a work day or not; that way, you can have variations in the schedule (e.g., schedule changes and
partial holidays).
CREATE TABLE  work_calendar
(   dt  DATE       PRIMARY KEY
                   CONSTRAINT  work_calendar_dt
                       CHECK (dt = TRUNC (dt))
,   day_type       VARCHAR2 (8)  NOT NULL
                   CONSTRAINT  work_calendar_day_type
                       CHECK ( day_type IN ( 'HOLIDAY'
                                           , 'WEEKEND'
                                           , 'WORK DAY'
,   start_time     DATE
,   end_time       DATE
,   work_hours     NUMBER
,   work_hours_since_1970     -- or some point earlier than you'll ever need
                   NUMBER
,   CONSTRAINT  work_calendar_start_time
        CHECK ( TRUNC (start_time) = dt)
,   CONSTRAINT  work_calendar_end_time
        CHECK ( TRUNC (end_time) = dt)
This will let you do a lot of the calculations you need without a function.