Date based on elapsed months

[Morten Hans Jensen]

I have been unable to find a solution to my problem.

I have a date of birth of children and I now want to find the specific date of which they turn 60 months of age.
How do I go about solving this?

[Ken Chui]

Welcome to Statalist.

In future, please try to follow the instruction on the FAQ (http://www.statalist.org/forums/help) and provide the sample data/format. Especially date because they come in so many formats and types. What I showed below assumes that it's been input as a date that Stata can understand. If that does not work, then we must see the data format.

clear
input bdate
22222
end

format bdate %td
gen date6m = bdate + (365.25*5)
format date6m %td

Results:

     +-----------------------+
     |     bdate      date6m |
     |-----------------------|
  1. | 03nov2020   03nov2025 |
     +-----------------------+

[Morten Hans Jensen]

Thank you very much Ken! I am very new to Stata and the forums. I use the td format.
It works great but I do not understand why some of them have a birthday that differs from the day they were born (sorry for the screenshot).

[Ken Chui]

Thank you very much Ken! I am very new to Stata and the forums. I use the td format.
It works great but I do not understand why some of them have a birthday that differs from the day they were born (sorry for the screenshot).

If you just want the year to be increased by 5:

clear
input bdate
22222
end

format bdate %td
gen date6m = mdy(month(bdate), day(bdate), year(bdate) + 5)
format date6m %td

[Morten Hans Jensen]

Thank you!
Works like a charm.

Easy fix but not for a newbie!

[William Lisowski]

Recent versions of Stata include some new functions for working with relative dates and durations.

help datetime_relative_dates
help datetime_durations

They can be useful in cases like this, provided you don't take the function name "birthday" too seriously,

. describe when

Variable      Storage   Display    Value
    name         type    format    label      Variable label
------------------------------------------------------------------------------------------------
when            float   %td                   

. list, clean

            when  
  1.   04jul2020  
  2.   28feb2020  
  3.   29feb2020  
  4.   01mar2020  

. generate plus5a = birthday(when,yofd(when)+5)

. generate plus5b = mdy(month(when), day(when), year(when) + 5)
(1 missing value generated)

. format %td plus5a plus5b

. list, clean

            when      plus5a      plus5b  
  1.   04jul2020   04jul2025   04jul2025  
  2.   28feb2020   28feb2025   28feb2025  
  3.   29feb2020   01mar2025           .  
  4.   01mar2020   01mar2025   01mar2025  

.