Writing Code for a function

I need to write a function named get15MinTimePeriod which receives a float as input. The float received by the function represents the timestamp (seconds since midnight) of an observation. The function must return the 15-min time period of the observation in HH:MM AM/PM format. The function should have the following name and parameters

get15MinTimePeriod(timestamp)

For example if the input is 300.125 then the function will return 12:00AM

and if the input is 26150.431 then the function will return 07:15AM