Arithmetic with Time

[Bob Schacht-3]

I have two date variables (Date of application, and Date of Eligibility),
and I want to compute a variable showing the difference between these two
dates in days. Obviously, I can compute (EligDate - AppDate), but then how
do I convert that number to "days"?

Thanks,
Bob Schacht

Robert M. Schacht, Ph.D. <[hidden email]>
Pacific Basin Rehabilitation Research & Training Center
1268 Young Street, Suite #204
Research Center, University of Hawaii
Honolulu, HI 96814

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[ViAnn Beadle]

Since a date is measured in seconds, divide by 24*60*60 or use the datediff
function which takes care of things like leap days and does all the
arithmetic to level of granularity you want.

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Bob
Schacht
Sent: Thursday, June 26, 2008 1:44 PM
To: [hidden email]
Subject: Arithmetic with Time

I have two date variables (Date of application, and Date of Eligibility),
and I want to compute a variable showing the difference between these two
dates in days. Obviously, I can compute (EligDate - AppDate), but then how
do I convert that number to "days"?

Thanks,
Bob Schacht

Robert M. Schacht, Ph.D. <[hidden email]>
Pacific Basin Rehabilitation Research & Training Center
1268 Young Street, Suite #204
Research Center, University of Hawaii
Honolulu, HI 96814

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[Richard Ristow]

At 03:44 PM 6/26/2008, Bob Schacht wrote:

>I have two date variables (Date of application, and Date of
>Eligibility), and I want to compute a variable showing the
>difference between these two dates in days.

Two ways:
CTIME.DAYS(EligDate - AppDate)
or
DATEDIFF(Appdate,Eligdate,"days")

The former will include any time difference as a fractional day difference.

"DATEDIFF" (SPSS 14 and later) is far more sophisticated than the
CTIME.xxx() functions and I can only refer you to its documentation
in the Command Syntax Reference.

You can also explicitly use of SPSS's representation of dates and
times as values in seconds, but I think it's less readable. Anyway,
equivalent to CTIME.DAYS is
(EligDate - AppDate)/(24*60*60)
or
(EligDate - AppDate)/86400

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[Norton, John]

Hi Bob,

Try the following command:

COMPUTE los = CTIME.DAYS(end_date - start_date).

HTH,

John Norton
SPSS Inc.


-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Bob Schacht
Sent: Thursday, June 26, 2008 3:44 PM
To: [hidden email]
Subject: Arithmetic with Time

I have two date variables (Date of application, and Date of Eligibility),
and I want to compute a variable showing the difference between these two
dates in days. Obviously, I can compute (EligDate - AppDate), but then how
do I convert that number to "days"?

Thanks,
Bob Schacht

Robert M. Schacht, Ph.D. <[hidden email]>
Pacific Basin Rehabilitation Research & Training Center
1268 Young Street, Suite #204
Research Center, University of Hawaii
Honolulu, HI 96814

=====================
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For a list of commands to manage subscriptions, send the command
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[Peck, Jon]

To which I might add that the Date and Time Wizard on the Transform menu will walk you through all these nuances and can leave you with freshly minted purpose-built syntax.

Regards,
Jon Peck

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Richard Ristow
Sent: Thursday, June 26, 2008 2:25 PM
To: [hidden email]
Subject: Re: [SPSSX-L] Arithmetic with Time

At 03:44 PM 6/26/2008, Bob Schacht wrote:

>I have two date variables (Date of application, and Date of
>Eligibility), and I want to compute a variable showing the
>difference between these two dates in days.

Two ways:
CTIME.DAYS(EligDate - AppDate)
or
DATEDIFF(Appdate,Eligdate,"days")

The former will include any time difference as a fractional day difference.

"DATEDIFF" (SPSS 14 and later) is far more sophisticated than the
CTIME.xxx() functions and I can only refer you to its documentation
in the Command Syntax Reference.

You can also explicitly use of SPSS's representation of dates and
times as values in seconds, but I think it's less readable. Anyway,
equivalent to CTIME.DAYS is
(EligDate - AppDate)/(24*60*60)
or
(EligDate - AppDate)/86400

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[Bob Schacht-3]

At 10:25 AM 6/26/2008, Richard Ristow wrote:

>At 03:44 PM 6/26/2008, Bob Schacht wrote:
>
>>I have two date variables (Date of application, and Date of Eligibility),
>>and I want to compute a variable showing the difference between these two
>>dates in days.
>
>Two ways:
>CTIME.DAYS(EligDate - AppDate)
>or
>DATEDIFF(Appdate,Eligdate,"days")
>
>The former will include any time difference as a fractional day difference.
>
>"DATEDIFF" (SPSS 14 and later) is far more sophisticated than the
>CTIME.xxx() functions and I can only refer you to its documentation in the
>Command Syntax Reference.

Thanks to you and ViAnne for pointing to DATEDIFF. I have SPSS 16, but am
more familiar with SPSS 12, which lacks this function. DateDiff is perfect
for my needs. But I should have thought of CTIME.DAYS myself.

Again, thanks to all for their replies.
Bob Schacht


>You can also explicitly use of SPSS's representation of dates and times as
>values in seconds, but I think it's less readable. Anyway, equivalent to
>CTIME.DAYS is
>(EligDate - AppDate)/(24*60*60)
>or
>(EligDate - AppDate)/86400

Robert M. Schacht, Ph.D. <[hidden email]>
Pacific Basin Rehabilitation Research & Training Center
1268 Young Street, Suite #204
Research Center, University of Hawaii
Honolulu, HI 96814

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