Working with data prior to 1960

[Garreth Gibney]

In Stata, I am aware that the numeric encoding that Stata uses is centred on the first millisecond of 01jan1960, that is, 01jan1960 00:00:00.000. However, the current data set I am using is centre around 1800-01-01 00:00:00, with date calculated as hours since this date. Can I change the numeric encoding that Stata uses to 1800-01-01 00:00:00 rather than 01jan1960 00:00:00.000?

Thanks.

[Maarten Buis]

no, you have to change the data instead. So here is an example of how to do that:

. clear

. input otherdate

     otherdate
  1. 0
  2. 15
  3. 23
  4. end

.
. //How many hours is there between 1-1-1800 and 1-1-1960
.  di clock("01 Jan 1800 00:00:00.000", "DMYhms")/(60*60*1000)
-1402512

.  
.  // so that is the number we need to add to move to 1-1-1960
.  // to measure it in milisecons instead of hours we need to multiply by 60*60*1000
.  // These are very large numbers, so remember to store it as double
.  
.  gen double newdate = (otherdate - 1402512)*60*60*1000

.  
.  // Let Stata show those numbers as date time that humans can read
.  format newdate %tc

.  
.  //admire the result
.  list

     +-------------------------------+
     | otherd~e              newdate |
     |-------------------------------|
  1. |        0   01jan1800 00:00:00 |
  2. |       15   01jan1800 15:00:00 |
  3. |       23   01jan1800 23:00:00 |
     +-------------------------------+

[Nick Cox]

There is nothing to stop you using your own units of hours from any origin you choose. What you miss out on then starts with the lack of a specific Stata display format. For display you could use a corresponding string variable, but it would be a little fiddly to code up.

Better on the whole to shift the origin, as Maarten Buis advises.

[Garreth Gibney]

no, you have to change the data instead. So here is an example of how to do that:

. clear

. input otherdate

otherdate
1. 0
2. 15
3. 23
4. end

.
. //How many hours is there between 1-1-1800 and 1-1-1960
. di clock("01 Jan 1800 00:00:00.000", "DMYhms")/(60*60*1000)
-1402512

.
. // so that is the number we need to add to move to 1-1-1960
. // to measure it in milisecons instead of hours we need to multiply by 60*60*1000
. // These are very large numbers, so remember to store it as double
.
. gen double newdate = (otherdate - 1402512)*60*60*1000

.
. // Let Stata show those numbers as date time that humans can read
. format newdate %tc

.
. //admire the result
. list

+-------------------------------+
| otherd~e newdate |
|-------------------------------|
1. | 0 01jan1800 00:00:00 |
2. | 15 01jan1800 15:00:00 |
3. | 23 01jan1800 23:00:00 |
+-------------------------------+

Thanks, this works!