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Re: st: First date


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: First date
Date   Thu, 31 Jan 2013 11:55:59 +0000

To put it more simply: -ndate_added- looks like a daily date. You need
to convert that to a date-time in milliseconds before you can add it
to the time of day in milliseconds. The factor is 24 * 60 * 60 * 1000.

Nick

On Thu, Jan 31, 2013 at 11:53 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> Date-times for dates and times around now are in trillions (10^12 or
> so) of milliseconds
>
> . di %14.0f clock("02-Sep-2012 10:30:14", "DMYhms")
>  1662201014000
>
> so something is wrong with your variable -ndate_added-, because the
> values you have are far too small.
>
> More generally, what you should be doing is to add
>
> date-time in milliseconds = date in milliseconds + time of day in milliseconds
>
> but I guess what you are doing is adding
>
> date-time in milliseconds = date in some other units + time in milliseconds
>
> which won't work.
>
> Note also that whatever display format you assigned to -ndate_added-
> is quite immaterial; it's the numeric values underneath that format
> that your calculation uses.
>
> Nick
>
> On Thu, Jan 31, 2013 at 11:31 AM, Keniajin Wambui <kiangati@gmail.com> wrote:
>> I am using stataIC 12.1 64bit on windows 7.
>> I am calculating the first date the values for a given serial number
>> given was entered
>> The data example is
>>
>> time_done    ndate_added    serialNumber    dfst
>> 8:01:50 PM    26-Feb-09    88358        72127954
>> 4:56:27 PM    27-Feb-09    88358        61004955
>> 12:30:27 PM    25-Mar-09    88358        45044981
>> 10:30:14 PM    02-Sep-12    88358        81033238
>>
>>
>> I am using the following code but its giving me (12:30:27 PM
>> 25-Mar-09    88358)  as the first data to be entered but according to
>> the data (8:01:50 PM    26-Feb-09    88358) was the first to be
>> entered.
>>
>>     gen double timefst=clock(time_done, "hms")
>>     replace timefst=clock(time_done, "hm") if timefst==.
>>     format timefst %tc
>>     format ndate_added %tc
>>     gen dfst=ndate_added + timefst
>>     egen double fdoadd = min(dfst), by(serialNumber)
>>
>> how can I solve the problem
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