How do I sum 15 years to my dataset?
original dataset
dates val
1 2001-01-12 1.2
2 2001-02-12 1.2
3 2001-03-12 1.2
result
dates val
1 2016-01-12 1.2
2 2016-02-12 1.2
3 2016-03-12 1.2