operator < method
Compares two JDate base on their microsecondsSinceEpoch (millisecondsSinceEpoch if running on js environment)
Implementation
bool operator <(JDate other) => isJs
? _millisecondsSinceEpoch > other.millisecondsSinceEpoch
: _microsecondsSinceEpoch > other.microsecondsSinceEpoch;