Converting dates to numeric variables

[Marika Jalovaara]

Dear Stata folks,
I have a need to convert Stata dates (currently in %td format) to numeric variables showing year and month YYYYMM. I don't seem to find a way, so any help is very much appreciated.

-Marika

[Clyde Schechter]

I'm not entirely sure what you mean, but I think this will do what you want:

gen int new_monthly_date = mofd(date_variable_I_already_have)
format new_monthly_date %td

If you use date and time variables with any frequency in your work, it is well worth your time and effort to study the Date and time functions section of the [FN] manual.

[Nick Cox]

Clyde: Typo: the format should be %tm, because what you create is a monthly date variable.

[Marika Jalovaara]

Sorry for being unclear. I have Stata date variables but now the dates (at the precision of a month) need to be taken to another program in the form YYYYMM (year and month).
For instance I need to convert
15apr1985 to 198504
15jan1999 to 199901
15dec2004 to 200412
etc.

[Clyde Schechter]

Nick Cox Thanks for picking that up. Yes, I meant %tm.

Marika Jalovaara So this is a little different:

gen int year = yofd(date_variable_I_already_have)
gen int month = mofd(date_variable_I_already_have)
gen long variable_for_other_program = 100*year + month

[Marika Jalovaara]

Thank you Clyde! That one was the answer. All I had to do is replace the "mofd" with "month".

[Clyde Schechter]

Marika, you are right. My mofd() was an error, and month() was correct. Glad you figured it out despite my mistake.

[Nick Cox]

You could do it in one line, interesting for anyone paid according to the reciprocal of the number of lines they write.

. di real(string(mofd(daily("15apr1985", "DMY")), "%tmCYN"))
198504

I think that translates to

gen variable_for_other_program = real(string(mofd(date_variable_I_already_have), "%tmCYN"))