getTimeZone method
获取当前时间系统的本地时区
Implementation
double getTimeZone() {
DateTime local = DateTime.now();
DateTime localUtc = local.toUtc();
DateTime nowUtc = DateTime.utc(local.year, local.month, local.day,
local.hour, local.minute, local.second);
DateTime utc = DateTime.utc(localUtc.year, localUtc.month, localUtc.day,
localUtc.hour, localUtc.minute, localUtc.second);
Duration d = nowUtc.difference(utc);
return d.inMinutes / 60.0;
}