sanitizeToString method
Implementation
@override
String sanitizeToString() {
final res = StringBuffer();
final absOffset = value.abs();
final minutes = absOffset.inMinutes - (absOffset.inHours * 60);
final hours = absOffset.inHours + (minutes == 60 ? 1 : 0);
if (value.isNegative) res.write("-");
res.write("$hours".padLeft(2, "0"));
res.write(minutes == 60 ? "00" : "$minutes".padLeft(2, "0"));
return res.toString();
}