private void appendTimezone(StringBuilder r)
{
int offset = tzOffset;
char sign;
if (offset < 0)
{
sign = '-';
offset *= -1;
}
else
{
sign = '+';
}
int offsetHours = offset / 60;
int offsetMins = offset % 60;
r.AppendFormat(CultureInfo.InvariantCulture, "{0}{1:D2}{2:D2}", sign, offsetHours, offsetMins);
}