What does this question have to do with counter hardware? Are you accumulating pulses over time?
You need to provide some details. You haven't even said what language you are using or the specific hardware (assuming you are actually using a counter device).
I need to insert a number into an array for every 15mins continuously..and the array need to hold all datas for example in 0th position i insert a value 10 by 10.00am, after that at 1st position i need to insert 11 by 10.15am, next at 2nd position i need to insert 12 by 10.30am and so on...how this can be done
So, you really aren't using a hardware counter and you posted to this board by mistake.
Repost to the appropriate software board. You still have not provided the essential information of what language you are using. Why would you keep that secret?