Add seconds/minutes/hour to a datetime stata

[Marvin Aliaga]

Hello everyone,

Let's say that I have a date/time variable (vardt) formatted as %tc. how can I add one second to the variable. For example, if the vardt is 12jan2015 17:01:11, I need 12jan2015 17:01:12. Also how can I add 1 minute and hours?

Thank you in advance,
Marvin

[William Lisowski]

The output of help datetime tells us that the values of datetime variables are stored as

milliseconds since 01jan1960 00:00:00.000

Thus, adding 1000 to a datetime values increases it by one second; adding 60,000, by 1 minute; adding 3,600,000, by 1 hour.

[Marvin Aliaga]

thank you William. I also found that you can add minutes , hours by using the following command replace START_DT= START_DT+ msofseconds(1)

[Nick Cox]

I find it easier to work out the number in question 1000, 60000, 60000*60, ..., as the case may be than to read help datetime to find the name of the function that returns the constant!

[Emiliano Carlevaro]

Just s a reference for future readers (or myself in the future).

Make sure your numeric (datetime) variable is double. Otherwise one loses precious precision.

Example. Create a time series of 15 min long blocks since 1996-01-03 07:45 hs. Then, the first observation is 08:00hs, then 08:15 hs, 08:30hs and so on.

For example, this will not work as intended.

set obs 3
gen DATETIME = _n *(60*15*1000) + clock("1996-01-03 07:45:00.0", "YMD hms")

results in

3/01/1996	08:00
3/01/1996	08:15
3/01/1996	08:31

Do you see that unexpected 08:31?

Specifying double as variable type corrects it.

set obs 3
gen double DATETIME = _n *(60*15*1000) + clock("1996-01-03 07:45:00.0", "YMD hms")

See help data_types and help datetime_translation##intro