# Re: st: Combining date and time into one variable.

 From "ippab ippab" To statalist@hsphsun2.harvard.edu Subject Re: st: Combining date and time into one variable. Date Sat, 29 Mar 2008 18:23:17 -0400

```Thanks a lot!

On Fri, Mar 28, 2008 at 6:55 PM, Svend Juul <SJ@soci.au.dk> wrote:
> ippab wrote:
>
>  I have two variables, one indicating date and another indicating time
>  of the day.  For example, date = 03/26/2008 and time = 17:31:30.  I am
>  wondering how I can combine these two variables into one variable so
>  that I can use the new "Datetime" variable for tis.
>
>  My understanding is that 'tis' command (for panel data or time series
>  analysis) only accepts one variable.  Since I have several
>  observations for a panel on the same day, I need to make sure both
>  date and time are used as the time variable.
>
>  =====================================================
>
>  In Stata 10 the numeric value of a date variable is the number of days
>  since 1 January 1960 , and the numeric value of a time variable is the
>  number of milliseconds since midnight. Before adding them, transform the
>  date to milliseconds.
>
>     . clear
>     . set obs 1
>     . gen date = mdy(3,26,2008)
>     . format date %tdNN/DD/CCYY
>     . gen time = hms(17,31,30)
>     . format time %tcHH:MM:SS
>     . list
>          +-----------------------+
>          |       date       time |
>          |-----------------------|
>       1. | 03/26/2008   17:31:30 |
>          +-----------------------+
>
>     . gen double datetime = date*24*60*60*1000 + time
>     . format datetime %tcNN/DD/CCYY_HH:MM:SS
>     . list
>          +---------------------------------------------+
>          |       date       time              datetime |
>          |---------------------------------------------|
>       1. | 03/26/2008   17:31:30   03/26/2008 17:31:30 |
>          +---------------------------------------------+
>
>
>  Hope this helps
>
>
> Svend
>
>  ________________________________________________________
>
>  Svend Juul
>  Institut for Folkesundhed, Afdeling for Epidemiologi
>  (Institute of Public Health, Department of Epidemiology)
>  Vennelyst Boulevard 6
>  DK-8000 Aarhus C,  Denmark
>  Phone, work:   +45 8942 6090
>  Phone, home:   +45 8693 7796
>  Fax:           +45 8613 1580
>  E-mail:        sj@soci.au.dk
>  _________________________________________________________
>
>
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>
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```