add abstract method

Date add({
  1. int years = 0,
  2. int months = 0,
  3. int days = 0,
})

makes a new date instance and add days, months and years separately

Original date object remains unchanged

Note: It does not make any conversion, it simply adds to each field value and changes ALL at once

This Method is NOT safe for month and day bounds

Recommended: Use separate add*() methods

Implementation

Date add({int years = 0, int months = 0, int days = 0});