Difference in dates to deduce months

[Melyn Oluoch]

Hello everyone!

I would really appreciate help on the below.

I would like to find the difference between one variable named "Birthyear_C" (with e.g. 1985m5) and 2019m1 which is Jan 2019 and in doing so generate the number of months and round it up for my analysis of an event study model. I have provided my simple command and data below. The error reads "2019m1 invalid name". I have gone through help datetime but still can't figure out how to transform the 2019m1 to a Stata "month count" format. 21550 for example represents the count of days from 1.1.1960 to 1.1.2019 but I only want to calculate the months since my "Birthyear_C" only has month and year.

g montht = round(birthyear_C-2019m1)

* Example generated by -dataex-. For more info, type help dataex
clear
input byte b1_ int b2_ float birthyear_C
 5 -29 328
 7 -29 330
 9 -29 332
10 -29 333
11 -29 334
11 -29 334
12 -29 335
12 -29 335
 1 -28 336
 2 -28 337
 2 -28 337
 2 -28 337
 2 -28 337
 2 -28 337
 2 -28 337
 2 -28 337
 3 -28 338
 3 -28 338
 3 -28 338
 4 -28 339
 5 -28 340
 5 -28 340
 6 -28 341
 7 -28 342
 7 -28 342
 7 -28 342
 7 -28 342
 7 -28 342
 7 -28 342
 8 -28 343
 8 -28 343
 8 -28 343
 8 -28 343
 8 -28 343
 8 -28 343
 8 -28 343
 9 -28 344
10 -28 345
10 -28 345
10 -28 345
11 -28 346
11 -28 346
12 -28 347
12 -28 347
 1 -27 348
 1 -27 348
 2 -27 349
 2 -27 349
 2 -27 349
 2 -27 349
 2 -27 349
 3 -27 350
 3 -27 350
 3 -27 350
 4 -27 351
 4 -27 351
 4 -27 351
 4 -27 351
 5 -27 352
 5 -27 352
 5 -27 352
 5 -27 352
 6 -27 353
 6 -27 353
 6 -27 353
 6 -27 353
 6 -27 353
 7 -27 354
 7 -27 354
 7 -27 354
 7 -27 354
 7 -27 354
 8 -27 355
 8 -27 355
 8 -27 355
 8 -27 355
 8 -27 355
 8 -27 355
 8 -27 355
 9 -27 356
 9 -27 356
 9 -27 356
10 -27 357
10 -27 357
10 -27 357
10 -27 357
10 -27 357
11 -27 358
11 -27 358
11 -27 358
11 -27 358
11 -27 358
11 -27 358
11 -27 358
12 -27 359
12 -27 359
12 -27 359
12 -27 359
12 -27 359
12 -27 359
end
format %tm birthyear_C

[Andrew Musau]

g montht = birthyear_C-tm(2019m1)

I don't see the logic of rounding here. The result is in integer months.

help  tm()

[Clyde Schechter]

gen montht = birthyear_C - tm(2019m1)

I don't understand the point of -round()- here. Both birtheyar_C and tm(2019m1) are integers--there is nothing to round.

Added: Crossed with #2.

[Melyn Oluoch]

Thanks a lot Andrew Musau and Clyde Schechter. Yes, the months are whole numbers and don't need rounding.