# SPSS Date Function "Years" versus "Months"

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## SPSS Date Function "Years" versus "Months"

 So I am generating age related data on a recurring basis, primarily on an annual basis and sometimes more frequently and entails "Mean" and "Median" ages.  Historically, I have calculated age in fractional amounts......e.g., using the SPSS datediff function using "months" and dividing by 12 for the fractional component as I believe a median of 6.8 years is a relevant comparison to a subsequent year's 6.1 years.  I have colleagues who believe the SPSS datediff function using "years" is adequate.  I suppose they believe the mean age will result in a fractional component and yield or present a meaningful change in age if it occurs.  Any thoughts would be appreciated. ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
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## Re: SPSS Date Function "Years" versus "Months"

 Any calculation based on age last birthday needs to add 0.5 years. John F Hall  MA (Cantab) Dip Ed (Dunelm) [Retired academic survey researcher] Email:          [hidden email] Website:     Journeys in Survey Research Course:       Survey Analysis Workshop (SPSS) Research:   Subjective Social Indicators (Quality of Life) -----Original Message----- From: SPSSX(r) Discussion <[hidden email]> On Behalf Of SUBSCRIBE SPSSX-JohnF Sent: 02 July 2018 16:44 To: [hidden email] Subject: SPSS Date Function "Years" versus "Months" So I am generating age related data on a recurring basis, primarily on an annual basis and sometimes more frequently and entails "Mean" and "Median" ages.  Historically, I have calculated age in fractional amounts......e.g., using the SPSS datediff function using "months" and dividing by 12 for the fractional component as I believe a median of 6.8 years is a relevant comparison to a subsequent year's 6.1 years.  I have colleagues who believe the SPSS datediff function using "years" is adequate.  I suppose they believe the mean age will result in a fractional component and yield or present a meaningful change in age if it occurs.  Any thoughts would be appreciated. ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
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## Re: SPSS Date Function "Years" versus "Months"

 I designed DATEDIFF and DATESUM.DATEDIFF calculates the difference between two dates truncating any fractional part, so, for example, a unit of "years" returns a whole number of years.  Think of it as the answer to "are you old enough to drink".  The reason for the truncation is that the fractional part would be ambiguous, because years and months vary in length, so what exactly does .5 years mean?You can use "days" to get an exact difference, which will also have no fractional part assuming there is no time component.On Mon, Jul 2, 2018 at 8:49 AM John F Hall <[hidden email]> wrote:Any calculation based on age last birthday needs to add 0.5 years. John F Hall  MA (Cantab) Dip Ed (Dunelm) [Retired academic survey researcher] Email:          [hidden email] Website:     Journeys in Survey Research Course:       Survey Analysis Workshop (SPSS) Research:   Subjective Social Indicators (Quality of Life) -----Original Message----- From: SPSSX(r) Discussion <[hidden email]> On Behalf Of SUBSCRIBE SPSSX-JohnF Sent: 02 July 2018 16:44 To: [hidden email] Subject: SPSS Date Function "Years" versus "Months" So I am generating age related data on a recurring basis, primarily on an annual basis and sometimes more frequently and entails "Mean" and "Median" ages.  Historically, I have calculated age in fractional amounts......e.g., using the SPSS datediff function using "months" and dividing by 12 for the fractional component as I believe a median of 6.8 years is a relevant comparison to a subsequent year's 6.1 years.  I have colleagues who believe the SPSS datediff function using "years" is adequate.  I suppose they believe the mean age will result in a fractional component and yield or present a meaningful change in age if it occurs.  Any thoughts would be appreciated. ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD -- Jon K Peck[hidden email] ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
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## Re: SPSS Date Function "Years" versus "Months"

 I think we're at cross-purposes here.  Many surveys collect age last birthday: age 59 can be anywhere between 59 and 60 minus one day. A common error is to calculate the mean, and assume it is accurate, but it is more accurate to add 0.5. John F Hall  MA (Cantab) Dip Ed (Dunelm)[Retired academic survey researcher] Email:          [hidden email] Website:     Journeys in Survey Research From: SPSSX(r) Discussion <[hidden email]> On Behalf Of Jon PeckSent: 02 July 2018 18:20To: [hidden email]Subject: Re: SPSS Date Function "Years" versus "Months" I designed DATEDIFF and DATESUM. DATEDIFF calculates the difference between two dates truncating any fractional part, so, for example, a unit of "years" returns a whole number of years.  Think of it as the answer to "are you old enough to drink".  The reason for the truncation is that the fractional part would be ambiguous, because years and months vary in length, so what exactly does .5 years mean? You can use "days" to get an exact difference, which will also have no fractional part assuming there is no time component. On Mon, Jul 2, 2018 at 8:49 AM John F Hall <[hidden email]> wrote:Any calculation based on age last birthday needs to add 0.5 years.John F Hall  MA (Cantab) Dip Ed (Dunelm)[Retired academic survey researcher]Email:          [hidden email] Website:     Journeys in Survey ResearchCourse:       Survey Analysis Workshop (SPSS)Research:   Subjective Social Indicators (Quality of Life)-----Original Message-----From: SPSSX(r) Discussion <[hidden email]> On Behalf Of SUBSCRIBE SPSSX-JohnFSent: 02 July 2018 16:44To: [hidden email]Subject: SPSS Date Function "Years" versus "Months"So I am generating age related data on a recurring basis, primarily on an annual basis and sometimes more frequently and entails "Mean" and "Median" ages.  Historically, I have calculated age in fractional amounts......e.g., using the SPSS datediff function using "months" and dividing by 12 for the fractional component as I believe a median of 6.8 years is a relevant comparison to a subsequent year's 6.1 years.  I have colleagues who believe the SPSS datediff function using "years" is adequate.  I suppose they believe the mean age will result in a fractional component and yield or present a meaningful change in age if it occurs.  Any thoughts would be appreciated.=====================To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD=====================To manage your subscription to SPSSX-L, send a message to[hidden email] (not to SPSSX-L), with no body text except thecommand. To leave the list, send the commandSIGNOFF SPSSX-LFor a list of commands to manage subscriptions, send the commandINFO REFCARD -- Jon K Peck[hidden email]===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD
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## Re: SPSS Date Function "Years" versus "Months"

 Over the years there have been many discussions on this list. (archives before some year in the 90s are lost.) In many circumstances if one has control over the data gathering, it is better to ask data of birth.  Except for children, there is often less retrieval time to answer date of birth than there is to answer age. Many of us have to first recall what year it is now and then count on our fingers. ----- Art Kendall Social Research Consultants -- Sent from: http://spssx-discussion.1045642.n5.nabble.com/===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD Art Kendall Social Research Consultants