there is a hour during the night,

The Prophet sallallahu alayhe wa sallam said, "Indeed, there is a hour during the night, no Muslim man (woman) attains it asking Allah from the goods of the duniah and the akhirah except that Allah bestows it upon him (her), and that is every night" [Sahih Muslim]

*So, no need to stay up only 15th of Sha'ban to make dua to Allah to accept from you. Ok. You can do at any night of the year.