Requirement :  You want to schedule a job on specific day(s) of month and this job frequency can not be met with standard SM36 options.

Example : Your want to schedule a job for every 1st and 3rd Wednesday of month.

We will achieve our goal by creating a factory calendar and then use it for job scheduling in SAP.

Steps:

Go to target SAP system and execute transaction SCAL.

Click on "Factory Calendar" under Subobjects and click on change button(pencil).

Click on "Create" button and enter Factory calendar ID name and description.

Also enter the "From Year" and  "To Year" information. Press Save.

You will be prompted with transport related information for factory calendar , read it and acknowledge it by pressing enter.

Now , press Special Rules button to specify dates for which you want the calendar to be active. 

(In our case- create one special rule for  every 1st and 3rd Wednesday of month) . Check the Workday check box on these dates.

Once you have created all the special rules for all the 1st and 3rd Wednesday s  between your calendar's "From Date " and "To Date" press SAVE .

 In our example  the years are 2013 and 2020.

 Now our calendar is created , we will now create our job and link this calendar.

Execute transaction  SM36 and create your job. Specify the program and variant name as per requirement . 

Now  press the "Start Condition" button and enter the job frequency as "DAILY" (Shown Below). 

Press "Restrictions" button and enter the details as below.

Press" Transfer" button  , SAVE and RELEASE the job.