Hi Prashant,
When scheduling the work order, if it falls on a week day (For Ex: Saturday / Sunday), system will try to propose next date. This is based on the factory calendar assigned to your work centre.
If the date falls on Friday, system will pick the date and starts scheduling, this will include your Saturday and sunday also. I am not sure how to change this scheduling to exclude week ends, may be you need to develop some custom logic.
Refer below document preferred by pete, gives some inlight your query.
FAQ: Maintenance Order Scheduling
Regards
Terence