How to get time and use SETENV variable for Time Zones and DST
See:
https://github.com/espressif/esp-idf/blob/master/examples/protocols/sntp/README.md
https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
Time-zones: https://github.com/nayarsystems/posix_tz_db/blob/master/zones.csv
GMTGMT-1, M3.4.0/1,M10.4.0/2 GMTGMT-1 is the name of the time zone GMT-1 is the abbreviation used when DST is off 1 hour is the time difference from GMT GMT is the abbreviation used when DST is on ,M3 is the third month .4 is the forth occurrence of the day in the month when DST starts .0 is Sunday /1 is the time in hours when DST starts ,M10 is the tenth month .4 is the forth occurrence of the day in the month when DST ends .0 is Sunday /2 is the time in hours when DST ends
// Set timezone to British DST setenv("TZ","GMTGMT-1,M3.4.0/01,M10.4.0/02",1);
See: https://www.timeanddate.com/time/zones/ for your country code