toICalString method
Implementation
String toICalString() {
final buffer = StringBuffer();
buffer.writeln('BEGIN:${isDaylight ? 'DAYLIGHT' : 'STANDARD'}');
buffer.writeln('DTSTART:${_formatDateTime(dateTime)}');
buffer.writeln('TZOFFSETTO:$timeZoneOffset');
buffer.writeln('END:${isDaylight ? 'DAYLIGHT' : 'STANDARD'}');
return buffer.toString();
}