Timezone / Location. How do I set my time zone correctly?

Blynk 2.0
1

A permanent time difference of 3 or more hours. I tried different options. Setup is one of these options.

local.setPosix(F("Europe/Moscow"));
  local.setLocation(F("Europe/Moscow"));
  local.setTime(10800);

char *t_zone[4] = {"tz_name", "iso",  "tz", "tz_rule"};
   Blynk.sendInternal("utc", "time");      // Unix timestamp (with msecs)
   Blynk.sendInternal("utc", t_zone[mass]);

I change these values. There is always a difference of 3 hours. How and where to choose a time zone?

BLYNK_WRITE(InternalPinUTC) {
    String cmd = param[0].asStr();
    if (cmd == "time") {
        uint64_t utc_time = param[1].asLongLong();
         UTC.setTime(utc_time / 1000, utc_time % 1000); 
    } 
 //   else if (cmd == "iso") {
  //      String iso_time = param[1].asStr();
  //  } 
  else if (cmd == "tz") {
        String tz_offset = param[1].asStr();
        local.setPosix(F("Europe/Moscow"));
        long dst_offset = param[2].asInt();
    } 
    else if (cmd == "tz_name") {
        String tz_name = param[1].asStr();
        local.setPosix(F("Europe/Moscow"));
    }
   else if (cmd == "tz_rule") { 
        String tz_rule = param[1].asStr();
        local.setPosix(F("Europe/Moscow"));
     }
2

@hugiboss317 Please edit your post, using the pencil icon at the bottom, and add triple backticks at the beginning and end of your code so that it displays correctly.
Triple backticks look like this:
```

Copy and paste these if you can’t find the correct symbol on your keyboard.

Pete.