You want to receive a table showing the timestamp and max value for each day, correct?
In this example, I have calculated the maximum daily energy demand for each region for the time window selected, and listed in a table the Date & Hour for each region when this max value occurred (as well as the actual peak demand). Maybe that will provide some guidance?
Also, if you need to know the timestamp where the max value is obtained, using this function may help. More here.