age method
Returns the age by subtracting the current DateTime from until
if until
is null, it will be defaulted to today's date
returns null if the DateTime is null.
String? dateStr = '2000-10-10';
int? theAge = dateStr.toDateTime().age();
Implementation
int? age({DateTime? until}) {
if (this == null) return null;
DateTime cur = this!;
DateTime to = until ?? DateTime.now();
int age = to.year - cur.year;
if (cur.month <= to.month && cur.day < to.day) {
age--;
}
return age;
}