%Z is replaced by the timezone name or abbreviation, or by no characters if no time zone is determinable.

time_t rawtime = 1480685759; // Fri, 02 Dec 2016 13:35:59 GMT
struct tm * timeinfo;
timeinfo = (struct tm*)localtime(&rawtime); // Convert time_t to tm as UTC time
char buffer [80];

strftime (buffer,80,"%I:%M%p",timeinfo);
puts (buffer); // 01:35PM

strftime (buffer,80,"%H:%M:%S%p",timeinfo);
puts (buffer); // 13:35:59PM

strftime (buffer,80,"%H:%M:%S",timeinfo);
puts (buffer); // 13:35:59

strftime (buffer,80,"%d.%m.%y",timeinfo);
puts (buffer); // 02.12.16

strftime (buffer,80,"%a_%A",timeinfo);
puts (buffer); // Fri_Friday

strftime (buffer,80,"%b_%B",timeinfo);
puts (buffer); // Dec_December

strftime (buffer,80,"%c",timeinfo);
puts (buffer); // 02 Dec 2016 13:35:59

strftime (buffer,80,"%j",timeinfo);
puts (buffer); // 337 (day of the year as a decimal number (001-366))

strftime (buffer,80,"%W",timeinfo);
puts (buffer); // 48 (the week number of the year (Monday as the first day))

strftime (buffer,80,"%x",timeinfo);
puts (buffer); // 02 Dec 2016

strftime (buffer,80,"%X",timeinfo);
puts (buffer); // 13:35:59

strftime (buffer,80,"%y",timeinfo);
puts (buffer); // 16 (year without century).

strftime (buffer,80,"%Y",timeinfo);
puts (buffer); // 2016 (year with century)

strftime (buffer,80,"%Z",timeinfo);
puts (buffer); // ???