Function TimezoneIANA

coderd/util/tz/tz_windows.go:24–55

TimezoneIANA attempts to determine the local timezone in IANA format. If the TZ environment variable is set, this is used. Otherwise, /etc/localtime is used to determine the timezone. Reference: https://stackoverflow.com/a/63805394 On Windows platforms, instead of reading /etc/localtime, powershell

()

// is used instead to get the current time location in IANA format.
// Reference: https://superuser.com/a/1584968
func TimezoneIANA() (*time.Location, error) {
	loc, err := locationFromEnv()
	if err == nil {
		return loc, nil
	}
	if !xerrors.Is(err, errNoEnvSet) {
		return nil, xerrors.Errorf("lookup timezone from env: %w", err)
	}

	// https://superuser.com/a/1584968
	cmd := exec.Command("powershell.exe", "-NoLogo", "-NoProfile", "-NonInteractive")
	// Powershell echoes its stdin so write a newline
	cmd.Stdin = strings.NewReader(cmdTimezone + "\n")

	outBytes, err := cmd.CombinedOutput()
	if err != nil {
		return nil, xerrors.Errorf("execute powershell command %q: %w", cmdTimezone, err)
	}

	outLines := strings.Split(string(outBytes), "\n")
	if len(outLines) < 2 {
		return nil, xerrors.Errorf("unexpected output from powershell command %q: %q", cmdTimezone, outLines)
	}
	// What we want is the second line of output
	locStr := strings.TrimSpace(outLines[1])
	loc, err = time.LoadLocation(locStr)
	if err != nil {
		return nil, xerrors.Errorf("invalid location %q from powershell: %w", locStr, err)
	}

	return loc, nil
}