Its a lot of trouble to make the seconds into date according to the different days each year and some times the leap years.
I don't see why. There is, in the Time library, a function to set the time based on the number of seconds sine Jan. 1, 1970. That would be the value in epoch in the code you posted. Once you have done that, you simply call year(), month(), day(), hour(), minute(), and second().
There is a function to adjust the time. Set the time based on Greenwich mean time. Then, call adjustTime() with the offset for your local time, and let it deal with the fact that you don't live in Greenland.