[Nick Cox]

Indeed:

date != daily date

Stata dates = {date-time, daily date, weekly date, monthly date, quarterly date, half-yearly date, yearly date}

[Matthew Williams]

Dominik: You're replying to Clyde Schechter in #8. But #10 already pointed you to a solution, the numdate package from SSC.

clear
input long date
20141231
20180316
end

format date %8.0f

numdate daily newdate=date, pattern(YMD)
extrdate month month=newdate

list

+------------------------------+
| date newdate month |
|------------------------------|
1. | 20141231 31dec2014 12 |
2. | 20180316 16mar2018 3 |
+------------------------------+

Hi Nick,

How to extract month of birth in my case? the date format in my data is similar to the newdate variable in your example. I tried to use the following command but did not work. Thank you.

extrdate month month=newdate

Error

unknown function dofmonth()

Data

* Example generated by -dataex-. For more info, type help dataex
clear
input long birthdate
7683
4180
7967
6674
4612
8357
8594
7232
7537
9851
7630
5030
5063
8071
8331
8052
9090
6621
3778
3749
end
format %d birthdate

[Nick Cox]

I think the problem here is that you are using a legal but ancient and undocumented date display format. extrdate is not that flexible.

. format %td birthdate

. 
. extrdate month month=birthdate

works for me with your data example. This is the first time that''s been flagged in 4 years since the command was posted, and there is an easy fix as above, so I am not tempted to fix the code.

[Matthew Williams]

It works perfectly. Thank you.