Chapter 8: Dates, Times, and Intervals


About SAS Date, Time, and Datetime Values

Definitions

SAS date value

  • is a value that represents the number of days between January 1, 1960, and a specified date. SAS can perform calculations on dates ranging from A.D. 1582 to A.D. 19,900. Dates before January 1, 1960, are negative numbers; dates after are positive numbers .

    • SAS date values account for all leap year days, including the leap year day in the year 2000.

    • SAS date values can reliably tell you what day of the week a particular day fell on as far back as September 1752, when the calendar was adjusted by dropping several days. SAS day-of-the-week and length-of-time calculations are accurate in the future to A.D. 19,900.

    • Various SAS language elements handle SAS date values: functions, formats and informats.

SAS time value

  • is a value representing the number of seconds since midnight of the current day. SAS time values are between 0 and 86400.

SAS datetime value

  • is a value representing the number of seconds between January 1, 1960 and an hour /minute/second within a specified date.

The following figure shows some dates written in calendar form and as SAS date values.

click to expand
Figure 8.1: How SAS Converts Calendar Dates to SAS Date Values

Two-Digit and Four-Digit Years

SAS software can read two-digit or four-digit year values. If SAS encounters a two-digit year, the YEARCUTOFF= option can be used to specify which century within a 100 year span the two-digit year should be attributed to. For example, YEARCUTOFF=1950 means that two-digit years 50 through 99 correspond to 1950 through 1999, while two-digit years 00 through 49 correspond to 2000 through 2049. Note that while the default value of the YEARCUTOFF= option in Version 8 of the SAS System is 1920, you can adjust the YEARCUTOFF= value in a DATA step to accommodate the range of date values you are working with at the moment. To correctly handle 2-digit years representing dates between 2000 and 2099, you should specify an appropriate YEARCUTOFF= value between 1901 and 2000. For more information, see the 'YEARCUTOFF= System Option' in SAS Language Reference: Dictionary .

The Year 2000

Using the YEARCUTOFF= System Option

SAS software treats the year 2000 like any other leap year. If you use two-digit year numbers for dates, you'll probably need to adjust the default setting for the

YEARCUTOFF= option to work with date ranges for your data, or switch to four-digit years. The following program changes the YEARCUTOFF= value to 1950. This change means that all two digit dates are now assumed to fall in the 100-year span from 1950 to 2049.

 options yearcutoff=1950;  data _null_;     a='26oct02'd;     put 'SAS date='a;     put 'formatted date='a date9.;  run; 

The PUT statement writes the following lines to the SAS log:

 SAS date=15639  formated date=26OCT2002 

Note: Whenever possible, specify a year using all four digits. Most SAS date and time language elements support four digit year values.

Example: How YEARCUTOFF= Affects Two and Four-Digit Years

The following example shows what happens with data that contains both two and four-digit years. Note how the YEARCUTOFF= option is set to 1920.

 options yearcutoff=1920 nodate pageno=1 linesize=80 pagesize=60;  data schedule;     input @1 jobid $ @6 projdate mmddyy10.;     datalines;  A100 01/15/25  A110 03/15/2025  A200 01/30/96  B100 02/05/00  B200 06/15/2000  ;  proc print data=schedule;     format projdate mmddyy10.;  run; 

The resulting output from the PROC PRINT statement looks like this:

Output 8.1: Output from The Previous DATA Step Showing 4-Digit Years That Result from Setting YEARCUTOFF= to 1920
start example
 The SAS System            1  Obs    jobid      projdate   1     A100     01/15/1925   2     A110     03/15/2025   3     A200     01/30/1996   4     B100     02/05/2000   5     B200     06/15/2000 
end example
 

Here are some facts to note in this example:

  • In the datalines in the DATA step, the first record contains a two-digit year of 25, and the second record contains a four-digit year of 2025. Because the YEARCUTOFF= system option is set to 1920, the two-digit year defaults to a year in the 1900s in observation number 1. The four-digit year in observation number 2 is unaffected by the YEARCUTOFF= option.

  • The third record is similar to the first and defaults to a year in the 1900s based on the value of YEARCUTOFF=.

  • The output from records 4 and 5 shows results that are similar to records 1 and 2. The fourth record specifies a two-digit year of 00, and the fifth one specifies a four-digit year of 2000. Because of the value of the YEARCUTOFF= option, the years in the two resulting observations are the same.

As you can see, specifying a two-digit year may or may not result in the intended century prefix. The optimal value of the YEARCUTOFF= option depends on the range of the dates that you are processing.

In Releases 6.06 through 6.12 of SAS, the default value for the YEARCUTOFF= system option is 1900; in Version 7 and Version 8, the default value is 1920.

For more information on how SAS handles dates, see the section on dates, times and datetime values.

Practices That Help Ensure Date Integrity

The following practices help ensure that your date values are correct during all the conversions that occur during processing:

  • Store dates as SAS date values, not as simple numeric or character values.

  • Use the YEARCUTOFF= system option when converting two-digit dates to SAS date values.

  • Examine sets of raw data coming into your SAS process to make sure that any dates containing two-digit years will be correctly interpreted by the YEARCUTOFF= system option. Look out for

    • two-digit years that are distributed over more than a 100-year period. For dates covering more than a 100-year span, you must either use four digit years in the data, or use conditional logic in a DATA step to interpret them correctly.

    • two-digit years that need an adjustment to the default YEARCUTOFF= range. For example, if the default value for YEARCUTOFF= in your operating environment is 1920 and you have a two-digit date in your data that represents 1919, you will have to adjust your YEARCUTOFF= value downward by a year in the SAS program that processes this value.

  • Make sure that output SAS data sets represent dates as SAS date values.

  • Check your SAS programs to make sure that formats and informats that use two-digit years, such as DATE7., MMDDYY6., or MMDDYY8., are reading and writing data correctly.

Note: The YEARCUTOFF= option has no effect on dates that are already stored as SAS date values.

Working with SAS Dates and Times

Informats and Formats

The SAS System converts date, time and datetime values back and forth between calendar dates and clock times with SAS language elements called formats and informats .

  • Formats present a value, recognized by SAS, such as a time or date value, as a calendar date or clock time in a variety of lengths and notations.

  • Informats read notations or a value, such as a clock time or a calendar date, which may be in a variety of lengths, and then convert the data to a SAS date, time, or datetime value.

Date and Time Tools by Task

The following table correlates tasks with various SAS System language elements that are available for working with time and date data.

Table 8.1: Tasks with Dates and Times, Part 1

To do this

Use this

List

Input

Result

Write SAS date values in recognizable forms

Date formats

DATE w.

14686

17MAR00

   

DATE9.

14686

17MAR2000a

   

DAY w.

14686

17

   

DDMMYY w.

14686

17/03/00

   

DDMMYY10.

14686

17/03/2000

   

DDMMYYB w.

14686

17 03 00

   

DDMMYYB10.

14686

17 03 2000

   

DDMMYYC w.

14686

17:03:20

   

DDMMYYC10.

14686

17:03:2000

   

DDMMYYD w.

14686

17-03-00

   

DDMMYYD10.

14686

17-03-2000

   

DDMMYYN w.

14686

17MAR00

   

DDMMYYN10

14686

17MAR2000

   

DDMMYYP w.

14686

17.03.00

   

DDMMYYP10.

14686

17.03.2000

   

DDMMYYS w.

14686

17/03/00

   

DDMMYYS10.

14686

17/03/2000

   

DOWNAME.

14686

Friday

   

JULDAY w.

14686

77

   

JULIAN w.

14686

00077

   

MMDDYY w.

14686

03/17/00

   

MMDDYY10.

14686

03/17/2000

   

MMDDYYB w.

14686

03 17 00

   

MMDDYYB10. w.

14686

03 17 2000

   

MMDDYYC w.

14686

03:17:00

   

MMDDYYC10

14686

03:17:2000

   

MMDDYYD w.

14686

03-17-00

   

MMDDYYD10.

14686

03-17-2000

   

MMDDYYN w.

14686

031700

   

MMDDYYN10.

14686

03172000

   

MMDDYYP

14686

03.17.00

   

MMDDYYP10.

14686

03.17.2000

   

MMDDYYS

14686

03/17/00

   

MMDDYYS10.

14686

03/17/2000

   

MMYY. xw.

14686

03M2000

   

MMYYC w.

14686

03:2000

   

MMYYD.

14686

03-2000

   

MMYYN.

14686

032000

   

MMYYP.

14686

03.2000

   

MMYYS.

14686

03/2000

   

MONNAME.

14686

March

   

MONTH.

14686

3

   

MONYY.

14686

MAR2000

   

PDJULG w.

14686

2000077F

   

PDJULI w.

14686

0100077F

   

QTR w.

14686

1

   

QTRR w.

14686

I

   

TIME w.d

14686

4:04:46

   

TIMEAMPM w.d

14686

4:04:46 AM

   

TOD

14686

4:04:46

   

WEEKDATE w.

14686

Friday, March 17, 2000

   

WEEKDAY w.

14686

6

   

WORDDATE. w.

14686

March 17, 2000

   

WORDDATX w.

14686

17 MARCH 2000

   

YEAR w.

14686

2000

   

YYMM w.

14686

2000M03

   

YYMMC w.

14686

2000:03

   

YYMMDD w.

14686

2000-03

   

YYMMP w.

14686

2000.03

   

YYMMS.

14686

2000/03

   

YYMMN.

14686

200003

   

YYMMDD w.

14686

00-03-17

   

YYMON.

14686

2000MAR

   

YYQ xw.

14686

2000Q1

   

YYQC w.

14686

2000:1

   

YYQD w.

14686

2000-1

   

YYQP w.

14686

2000.1

   

YYQS w.

14686

2000/1

   

YYQN w.

14686

20001

   

YYQR w.

14686

2000QI

   

YYQRC w.

14686

2000:I

   

YYQRD w.

14686

2000-I

   

YYQRP w.w.

14686

2000.I

   

YYQRS w.

14686

2000/I

   

YYQRN w.

14686

III

Table 8.2: Tasks with Dates and Times, Part 2

To do this

Use this

List

Input

Result

Date Tasks

Read calendar dates as SAS date

Date informats

DATE w.

17MAR2000

14686

Note:

YEARCUTOFF=1920

   

DATE9.

17MAR2000

14686

   

DDMMYY w.

170300

14686

   

DDMMYY8.

17032000

14686

   

JULIAN w.

0077

14686

   

JULIAN7.

2000077

14686

   

MMDDYY w.

031700

14686

   

MMDDYY10.

03172000

14686

   

MONYY w.

MAR00

14670

   

YYMMDD w.

000317

14686

   

YYMMDD10.

20000317

14686

   

YYQ w.

00Q1

14610

Create date values from pieces

Date functions

DATEJUL

2000077

14686

   

DATETIME

'17MAR2000'D,

00,00,00

1268870400

   

TIME

14,45,32

53132

   

MDY

03,17,00

14686

   

MDY

03,17,2000

14686

   

YYQ

00,1

14610

Extract a date from a datetime value

Date functions

DATEPART

'17MAR00:00:00

'DT

14686

Return today's date as a SAS date

Date functions

DATE() or TODAY() (equivalent)

( )

SAS date for today

Extract calendar dates from SAS

Date functions

DAY

14686

17

   

HOUR

14686

4

   

JULDATE

14686

77

   

JULDATE7

14686

2000077

   

MINUTE

14686

4

   

MONTH

14686

3

   

QTR

14686

3

   

SECOND

14686

46

   

WEEKDAY

14686

6

   

YEAR

14686

2000

Write a date as a constant in an expression

SAS date constant

'ddmmmyy' d

or

'ddmmmyyyy'

'17mar00'd

'17mar2000'd

14686

Write today's date as a string

SYSDATE automatic macro variable

SYSDATE

&SYSDATE

Date attime of SAS initialization in DDMMMYY

 

SYSDATE9

SYSDATE9

&SYSDATE9

Date at time of SAS initialization in DDMMMYYYY

Time Tasks

Write SAS time values as time values

time formats

HHMM.

53132

14:46

   

HOUR.

53132

15

   

MMSS.

53132

885

   

TIME.

53132

14:45:32

   

TOD.

53132

14:45:32

Read time values as SAS time values

Time informats

TIME

14:45:32

53132

Write the current time as a string

SYSTIME automatic macro variable

SYSTIME

&SYSTIME

Time at momentof executionin HH:MM

Return the current time of day as a SAS time value

Time functions

TIME( )

( )

SAS time value at momentof executionin NNNNN.NN

Return the time part of a SAS datetime value

Time functions

TIMEPART

SAS datetime value in NNNNNNNNNN.N

SAS time value part of date value in NNNNN.NN

Datetime Tasks

Write SAS datetime values as datetime values

Datetime formats

DATEAMPM

1217083532

26JUL98:02:45

PM

   

DATETIME

1268870400

17MAR00:00:00

:00

Read datetime values as SAS datetime values

Datetime informats

DATETIME

17MAR00:00:00:00

1268870400

Return the current date and time of day as a SAS datetime value

Datetime functions

DATETIME()

()

SAS datetime value at momentof executionin NNNNNNNNNN.N

Interval Tasks

Return the number of specified time intervals that lie between the two date or datetime values

Interval functions

INTCK

week 2

01aug60

01jan01

1055

Advances a date, time, or datetime value by a given interval, and returns a date, time, or datetime value

Interval functions

INTNX

day

14086

01jan60

14086

The SAS System also supports international formats and informats that are equivalent to some of the most commonly used English-language date formats and informats. For details, see the SAS formats and informats in SAS Language Reference: Dictionary .

Examples

Example 1: Displaying Date, Time, and Datetime Values as Recognizable Dates and Times

The following example demonstrates how a value may be displayed as a date, a time, or a datetime. Remember to select the SAS language element that converts a SAS date, time, or datetime value to the intended date, time or datetime format. See the previous tables for examples.

Note:

  • Time formats count the number of seconds within a day, so the values will be between 0 and 86400.

  • DATETIME formats count the number of seconds since January 1, 1960, so for datetimes that are greater than 02JAN1960:00:00:01, (integer of 86401) the datetime value will always be greater than the time value.

  • When in doubt, look at the contents of your data set for clues as to which type of value you are dealing with.

This program uses the DATETIME, DATE and TIMEAMPM formats to display the value 86399 to a date and time, a calendar date, and a time.

 data test;  options nodate pageno=1 linesize=80 pagesize=60;  Time1=86399;  format Time1 datetime.;  Date1=86399;  format Date1 date.;  Time2=86399;  format Time2 timeampm.;  run;  proc print data=test;  title  'Same Number, Different SAS Values';  footnote1 'Time1 is a SAS DATETIME value';  footnote2 'Date1 is a SAS DATE value';  footnote3 'Time2 is a SAS TIME value'.;  run; 
Output 8.2: Datetime, Date and Time Values for 86399
start example
 Same Number, Different SAS Values             1  Obs         Time1           Date1        Time2   1     01JAN60:23:59:59    20JUL96    11:59:59 PM            Time1 is a SAS DATETIME value              Date1 is a SAS DATE value              Time2 is a SAS TIME value. 
end example
 

Example 2: Reading, Writing, and Calculating Date Values

This program reads four regional meeting dates and calculates the dates on which announcements should be mailed.

 data meeting;  options nodate pageno=1 linesize=80 pagesize=60;     input region $ mtg : mmddyy8.;     sendmail=mtg-45;     datalines;  N  11-24-99  S  12-28-99  E  12-03-99  W  10-04-99  ;  proc print data=meeting;     format mtg sendmail date9.;     title 'When To Send Announcements';  run; 
Output 8.3: Calculated Date Values: When to Send Mail
start example
 When To Send Announcements  Obs    region          mtg     sendmail   1       N       24NOV1999    10OCT1999   2       S       28DEC1999    13NOV1999   3       E       03DEC1999    19OCT1999   4       W       04OCT1999    20AUG1999 
end example
 



SAS 9.1 Language Reference. Concepts
SAS 9.1 Language Reference Concepts
ISBN: 1590471989
EAN: 2147483647
Year: 2004
Pages: 255

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