It might not work with daylight savings, it also might not work in
UTC-?? timezones.
from the sources:
snprintf(buffer, 256, "TZUTC: %02d%02d", offhour, offmin);
this will return somthing like -700 for negative timezones. I think this should
work better:
snprintf(buffer, 256, "TZUTC: %0*d%02d", (offhour < 0) ? 3 : 2, offhour, offmin);
* Origin: 🌈 (21:1/151)