There is always a cut off date mentioned in advertisement. I think in this case,for BS -17 computer operator job ,last date for submitting an application is considered to be a cut off date . If you are 6 months,or even a day younger than that date , then sadly you are not eligible for that post, and if not now , eventually you will get rejected sometime. Maybe during interviews ,maybe before joining the department.

But don't rely on this thing , you must contact Fpsc ,and ask them this query. I don't really know about cut off date for your post. Fpsc will answer this thing better.

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''Sufficient for us is Allah , and He is the best Disposer of affairs" Al-Quran