subtractYears method
Subtracts the specified number of years from the current DateTime.
NOTE: you WILL lose Feb 29th when adding and subtracting 1 year
Args: years (int): The number of years to subtract.
Returns: DateTime: A new DateTime object with the subtracted years.
Implementation
DateTime subtractYears(int years) {
if (years == 0) {
// same
return this;
}
// We used the Jiffy package to add years, months, etc
// https://stackoverflow.com/questions/54792056/add-subtract-months-years-to-date-in-dart
return Jiffy.parseFromDateTime(this).subtract(years: years).dateTime;
}