st: RE: Date conversion question

[Nick Cox <n.j.cox@durham.ac.uk>]

Don't apologise. If your question is reasonable, just post it. Otherwise, don't! 

Let's work through this step by step. 

Your -rssd9999- has values like 2e7. 

It's evidently a date-time measured in milliseconds. 

. di %tc 2e7
01jan1960 05:33:20

It is a date-time to you, but you need a sensible display format for it. In fact, you have one. 

Next off, -year()- is a function that maps daily dates to years. So, first you need to map date-times to days before you can call up -year()-. That is done by -dofc()-. The function calls can be nested: 

. di %td dofc(2e7)
01jan1960

. di %ty year(dofc(2e7))
1960

What's wrong is that -year()- looks at your variable and can only think that it's in days, indeed 2e7 days after 1 January 1960. That's about 55,000 years from now, and Stata isn't that far-sighted. 

Nick 
n.j.cox@durham.ac.uk 

Amy Dunbar

Sorry to bother the list with a trivial date question, but I can't figure out I read out how to solve my problem.
How do I get a date variable (rssd9999) to show the actual date instead of 2.01e+07?

I tried to pull out the year with
                         gen year = year(rssd9999)
but the generated variable is ".", so the commands suggested in the date and time help file don't work for this variable.

I show the results of tab and codebook for this variable below.

.               tab rssd9999

                Date      Freq.     Percent                Cum.
                                                                
                2.01e+07              1,218     4.47        4.47
                2.01e+07              5,689     20.88     25.35
                2.01e+07              1,208     4.43        29.78
                2.01e+07              5,669     20.80     50.58
                2.01e+07              1,208     4.43        55.01
                2.01e+07              5,516     20.24     75.26
                2.01e+07              1,215     4.46        79.71
                2.01e+07              5,528     20.29     100.00
                                                                
                Total      27,251   100.00

. codebook rssd9999

----------------------------------------------------------------------------------------------------------------------
rssd9999                                                                                                          Date
----------------------------------------------------------------------------------------------------------------------

                  type:  numeric (double)

                 range:  [20070331,20081231]          units:  1
         unique values:  8                        missing .:  0/27251

            tabulation:  Freq.  Value
                          1218  20070331
                          5689  20070630
                          1208  20070930
                          5669  20071231
                          1208  20080331
                          5516  20080630
                          1215  20080930
                          5528  20081231


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