What is %td.. ?

[johnkim]

Dear all,

Hi, I have a variable InceptionDate. When I run "d InceptionDate", I get

storage display value
variable name type format label variable label
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------
InceptionDate~S int %td.. Inception Date

I thought InceptionDate was an integer variable (e.g., 19990803), which I was intending to use to generate a %td variable. But the display format "%td.." appears to say it's already %td variable. But then again, it's not "%td". I'm not sure what to make of it.
I'd appreciate your help in how to interpret this or how to generate a %td variable. Thank you very much!

Best,
John

[Dimitriy V. Masterov]

In Stata, dates are usually stored as integers, with 01jan1960 as zero. Your example date would be 14459. When you change the display format of that integer to %td, it merely alters how that integer looks to you. For instance,

. di td(02may2015)
20210

. di %td 20210
02may2015

. di %tdM-D-Y 20210
      May-02-15

[johnkim]

Dear Dimitriy,
Thanks for your comment. I am aware of the display variations of %td, but I was not able to find what "%td.." means, which is why I'm not sure if that actually is a date variable. I'd appreciate your thoughts.
Thank you!

Best,
John

[Dimitriy V. Masterov]

I guess I did not connect all the dots. That's just Stata shorthand for a custom %td format that is too long to fit in the output of des:

. set obs 10
number of observations (_N) was 0, now 10

. gen date = 10000+_n

. format date %td

. clonevar date2=date

. format date2 %tdCCYYNNDD

. des

Contains data
  obs:            10                          
 vars:             2                          
 size:            80                          
--------------------------------------------------------------------------------------------------------------
              storage   display    value
variable name   type    format     label      variable label
--------------------------------------------------------------------------------------------------------------
date            float   %td                   
date2           float   %td..                 
--------------------------------------------------------------------------------------------------------------
Sorted by: 
     Note: Dataset has changed since last saved.

. list, clean noobs

         date      date2  
    20may1987   19870520  
    21may1987   19870521  
    22may1987   19870522  
    23may1987   19870523  
    24may1987   19870524  
    25may1987   19870525  
    26may1987   19870526  
    27may1987   19870527  
    28may1987   19870528  
    29may1987   19870529

[Marcos Almeida]

Dimitri has provided a thorough explanation.

I just wish to underline that John is supposed to use the - date() - function to create a date variable before editing the display of the date.

Best,

Marcos

[Dimitriy V. Masterov]

I am not sure that the -date()- advice right. I think John has a td variable formatted to look like an integer, mostly likely as %tdCCYYNNDD. The easiest way to learn what the format is to use the -varmanage- command to open the Variable Manager. That would give the full format, unlike -des-.