Re: st: date function

[Nick Cox <njcoxstata@gmail.com>]

Working backwards:

1. Changing the format of anything has precisely no effect on what is
stored, only on what is displayed. Thinking that "format" means
"display format" and nothing else is crucial to understanding this.
There is a Tip spelling this out in excruciating detail.

http://www.stata-journal.com/article.html?article=dm0067

So no machinations with -format- will solve this problem.

2. My guess is that your -date- variable is thoroughly messed up and
it was produced in some wild way. I guess further that you used
-encode- to convert a string variable into a numeric variable with
labels. If you look at the dates that Stata thinks are stored they are
all daily dates in 1960 and, moreover, the first such date in your
sample is

03/01/2003         10           1              1960

and the last such date is

25/04/2003         10           4              1960

which is consistent with this guess. That is, the string "03/01/2003"
is the first alphabetically (alphanumerically) and the string
"25/04/2003" is the last alphabetically in this sample and they, and
the other dates, have been mapped to numbers. -encode- is totally
clueless about dates and faced with dates it can only treat them like
any other set of strings, the first alphabetically being mapped to 1,
the second to 2, and so forth, regardless of the strings' meaning or
content.

So, you must go back and recalculate your dates, using the -date()-
function. Ironically, or otherwise, this is the title of your post,
but you appear not to have used it.

As said, these are guesses, but I'd call them informed guesses.

The document to read first, second and third on dates is the help.
-help dates and times-.

Nick
njcoxstata@gmail.com

On 6 August 2013 15:52, Dherani, Mukesh <M.K.Dherani@liverpool.ac.uk> wrote:

> I have a problem getting my date variable sorted.  I have Date variable in = my data (float) and I want month and year extracted using
>
> gen month = month(date)..... same for day and yr.
> However, I am getting incorrect values for month and year (even day).
> I have also tried formatting month and year to %m and %ty, but to no avail.
> Any help appreciated... I am using Stata 10. [no luck with FAQ so far]
>
>
> date               day         month            yr
> 19/02/2003         22           3              1960
> 17/01/2003         25           1              1960
> 03/01/2003         10           1              1960
> 23/01/2003         16           2              1960
> 03/01/2003         10           1              1960
> 07/01/2003         7              4              1960
> 10/01/2003         30           1              1960
> 18/07/2003         14           2              1960
> 25/04/2003         10           4              1960
> 05/04/2004         5              2              1960
> 03/01/2003         10           1              1960
> 19/06/2003         21           2              1960
> 13/06/2003         5              1              1960
> 19/08/2003         12           4              1960
>
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