Hi Atul,
SAP provides standard date types, date rules and durations which can be used for your scenario.
Please maintain duration (ex: SRV_RF_DURA) in date profile and maintain the same duration id in response profile in response time.
Maintain a date type for first response by (ex: SRV_RFIRST), assign a date rule (ex: SRV_0001) within it in date profile.
Maintain service profile as reference object in date profile, maintain the same in first response date type and check the current time in date type.
Maintain the first response date type in screen areas 'service' in date profile.
Hope it may help you.
Regards,
Maddy.