SPSS Date Time Functions

While dates and times are simply a formatted numeric data type in SPSS, a set of built-in functions are offered for these variables.

To clarify, these functions operate at case level. They do not perform higher-level computations.

Date

The DATE function returns a date value.

compute jan_2_3000 = date.mdy(1, 2, 3000)

Valid subtypes of the DATE function include...

• date.mdy(month, day, year) (shown above)

• date.dmy(day, month, year)

• date.moyr(month, year)

• date.qyr(quarter, year) where quarter is between 1 and 4

• date.wkyr(week, year) where week is between 1 and 53

• date.yrday(year, daynum) where daynum is between 1 and 366

These range checks are common to all of the above:

• year must be greater than 1582

• month must be between 1 and 13

• day must be between 0 and 31

Note that a date format must separately be applied to a created variable.

Note that if a range check is failed for any argument, a missing value is returned.

Note that if a day value is invalid for a particular month (eg. 29 through 31 for February in non-leap years) the returned value is placed in the next month. For example, date.mdy(9, 31, 2006) returns the date value for October 1, 2006.

Note that a day value of 0 returns the date value for the last day of the previous month.

Note that a month value of 13 is equivalent to January in the following year.

Note that for any year value, date.wkyr(1, year) will return January 1 of that year.

Datediff

The DATEDIFF function subtracts a date or time from another, returning an integer in terms of the specified unit.

num_days = datediff(date1,date2,"days")

Valid units include:

• "years"

• "quarters"

• "months"

• "weeks"

• "days"

• "hours"

• "minutes"

• "seconds"

Note that the returned value is floored using the specified unit.

Datesum

The DATESUM function adds some number of units to a date or time, returning a new date or time.

month_ago = datesum(date1,-1,"months")

Reference the above list for valid values of the third argument.

Time

The TIME function returns a time value.

compute two_thirty = time.hms(2, 30, 0)

Valid subtypes of the DATE function include...

• time.hms(hours, minutes, seconds) (shown above) where seconds is allowed to be a decimal

• time.hms(hours, minutes) where minutes is allowed to be a decimal

• time.hms(hours) where hours is allowed to be a decimal

• time.days(days)

Note that a time format must separately be applied to a created variable.

Note that minutes must be less than 60 if hours is non-zero. time.hms(0, 90) valid, but time.hms(1, 90) is not. Similarly, seconds must be less than 60 if minutes or hours are non-zero.

Xdate

The XDATE function extracts a component of a date or time value.

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