Announcement

Collapse
No announcement yet.
X
Collapse
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
  • #1

    Dealing with Date variables in Stata

    Hello, I am using Stata 16.1 (MP). I have a date variable, which is stored as a numeric variable in the data. When I -tab- the variable, it shows the following (it seems like a string variable):
    Click image for larger version Name: QQ20230107-154954@2x.png Views: 1 Size: 159.7 KB ID: 1696242

    But When I codebook this variable, it has numeric values associated with each date, as follows:
    Click image for larger version Name: QQ20230107-155349@2x.png Views: 1 Size: 120.1 KB ID: 1696243

    I googled and found it is the Stata formate for date. But I am not sure how to deal with this vairbale. For example, I would like to create a categorical variable based on this variable: people who complete their degree before a certain date.
    I was wondering if anyone could help with this question.
    Code:
    * Example generated by -dataex-. To install: ssc install dataex
clear
input int date
22671
22085
21903
21686
22264
    .
    .
21663
21451
    .
21626
21686
22095
    .
21762
22095
22280
21959
    .
21314
    .
    .
    .
22505
22234
    .
22125
21805
    .
22159
    .
    .
22049
21704
22188
21672
21501
20975
21901
21889
21609
21693
22431
22056
21906
21489
21532
21508
    .
22224
21686
    .
22592
22342
22096
21684
20951
22624
21726
21675
    .
22415
    .
    .
22599
22026
    .
21898
21745
21897
22043
21312
22144
22300
    .
    .
21677
21792
20963
21715
    .
21647
    .
    .
22234
    .
22090
21390
22123
    .
    .
22481
21924
    .
    .
22050
22097
22415
21684
21898
end
format %tdnn/dd/CCYY date
    Tags: None
  • #2
    You should consult

    Code:
    help datetime
    for an extensive treatment of date and time variables in Stata. The first sentence in the documentation answers a good part of your questions:


    Stata dates are numeric values that record durations (positive or negative) from 01jan1960.
    In any case, the display command can be used to translate SIF values to human-readable dates and vice versa, e.g.,

    Code:
    display %td 21898
display td(15dec2019)
    Res.:

    Code:
    . display %td 21898
15dec2019

. display td(15dec2019)
21898
    The -td()- function from above therefore makes it easier to type dates without knowing their underlying SIF values. See

    Code:
    help td()
    Last edited by Andrew Musau; 07 Jan 2023, 02:02.
    • 1 like

    Comment

    • #3
      Originally posted by Andrew Musau View Post
      You should consult

      Code:
      help datetime
      for an extensive treatment of date and time variables in Stata. The first sentence in the documentation answers a good part of your questions:




      In any case, the display command can be used to translate SIF values to human-readable dates and vice versa, e.g.,

      Code:
      display %td 21898
display td(15dec2019)
      Res.:

      Code:
      . display %td 21898
15dec2019

. display td(15dec2019)
21898
      The -td()- function from above therefore makes it easier to type dates without knowing their underlying SIF values. See

      Code:
      help td()
      Thank you so much, Andrew! It solves the problem. In case anyone has the same problem, what you need to do is to wrap the human readable dates using the brackets td() (as my date is stored in td format). In my example, if I would like to know someone who completed a degree before a certain date, I put this
      Code:
      date<td(02jul2019)
      instead of
      Code:
      date<02jul2019
      Using td() will help Stata to read the command.

      Comment

      • #4
        Code:
        ... if date < mdy(7, 2, 2019)
        is another way to do it.

        Comment

        • #5
          Originally posted by Nick Cox View Post
          Code:
          ... if date < mdy(7, 2, 2019)
          is another way to do it.
          Thank you, Nick

          Comment

          Previous Next
          Working...
          X