Date, Time, and Datetime Values

Question 1

Describe Date values

Answer 1

An integer representing the number of days since 1/1/1960 (day 0)

Question 2

Describe Time values

Answer 2

An integer representing the number of seconds since midnight

Question 3

Describe Datetime values

Answer 3

An integer representing the number of seconds since midnight of 1/1/1960

Question 4

Can Date values be used in arithmetic equations?

Answer 4

Yes. In SAS they are stored as integers and so can be used like integers.

Question 5

Difference between formats and informats

Answer 5

Informats read notations and convert them to SAS values, such as reading 16SEP2013 and converting it to 19617. Formats present a SAS value in a more user-readable way, such as presenting the date value of 19617 as 9/16/2013. Informats are IN to SAS, formats are OUT.

Question 6

Syntax to read data into SAS based on a certain informat

Answer 6

INPUT VariableName FormatType; (in the DATA step) Example, INPUT Birthdate ANYDTDTE9. If you have multiple variables, just put the next variable name after the format type.

Question 7

What delimeters can be used for date informats?

Answer 7

Almost any is allowed: slash (/), period (.), space ( ), underscore (_) dash (-), etc. However only 1 at a time is acceptable (ex. 9-16/13 will result in an error).

Question 8

Date Informat: ANYDTDTEw.

Answer 8

Reads dates in various formats. Examples, 1/1/1961, 1jan1961, etc. Default width of 9. For ambiguous dates like 01/02/01, SAS uses the DATASTYLE system option to set which should be read as the month, day, and year.

Question 9

Date Informat: DATEw.

Answer 9

Reads dates with the month in text form. Example, 1jan1961.

Question 10

Date Informat: DDMMYY.

Answer 10

Reads dates in all number form with the day listed before the month. Example, 26/09/2013.

Question 11

Date Informat: MMDDYYw.

Answer 11

Reads dates in all number form with the month listed before the day. Example, 9-26-2013.

Question 12

Syntax to display a variable as a certain format

Answer 12

FORMAT VariableName FormatType; (in the PROC step) Example, FORMAT Birthdate WORDDATE18.;

Question 13

Date Format: DATEw.

Answer 13

Fill in

Question 14

Date Format: DAYw.

Answer 14

Fill in

Question 15

Date Format: Monthw.

Answer 15

Fill in

Question 16

Date Format: Yearw.

Answer 16

Fill in

Question 17

Date Format: EURDFDDw.

Answer 17

Fill in

Question 18

Date Format: DDMMYYw.

Answer 18

Fill in

Question 19

Date Format: MMDDYYw.

Answer 19

Fill in

Question 20

Date Format: WEEKDATEw.

Answer 20

Fill in

Question 21

Date Format: WORDDATEw.

Answer 21

Fill in

Question 22

Date Format: DOWNAME.

Answer 22

Fill in

Question 23

Datetime Format: DATETIME

Answer 23

26JUL98:14:45:13

Question 24

Datetime Format: DATEAMPM

Answer 24

26JUL98:02:45 PM

Question 25

Time Format: TIME.

Answer 25

Fill in

Question 26

Time Format: TIMEAMPM.

Answer 26

Fill in

Question 27

Syntax to use a date as a constant

Answer 27

'Date'D; (in the DATA step) Example, '02AUG1983'D;

Question 28

Describe the YEARCUTOFF system option

Answer 28

It specifies the first year of the 100 year window for 2-digit years. For example, YEARCUTOFF=1920 (default) means 2-digit years run from 1920 to 2019.

Question 29

If you specify YEARCUTOFF, can you use 4-digit years?

Answer 29

Yes, in fact it's necessary for years outside of the 100 year window. For example, YEARCUTOFF=1920 means there is no way to enter a year of 2020 with 2-digits.

Question 31

Function to extract a date value from a datetime value

Answer 31

DATEPART

Question 32

Function to extract a time value from a datetime value

Answer 32

TIMEPART

Question 33

Function to return today's date

Answer 33

TODAY()

Question 34

Function to return the current time of day

Answer 34

TIME()

Question 35

Function to return the current date/time

Answer 35

DATETIME()

Question 36

Describe intervals

Answer 36

Intervals are a unit of measurement in SAS, e.g. days, weeks, months, and so forth. It is important to be aware that the starting point for intervals is not necessary equal to the date value itself. For example, SAS will count the months between 8/31/2013 and 9/1/2013 as 1 month, because the starting point of the interval is 8/1/2013, which is 1 month from 9/1/2013.

Question 37

Syntax for custom intervals

Answer 37

IntervalX.Y - Interval is the type of interval (MONTH, YEAR, etc.), X is a multiple of the interval (ex. YEAR5 will do intervals of 5 years) and Y is the starting point (ex. WEEK.2 will start weeks on Mondays instead of Sundays). X and Y are equal to 1 if they are not included.

Question 38

How does SAS determine the starting point of an interval?

Answer 38

Day intervals are set with 1/1/1960 as the start of the very first interval (or in the case of time intervals, midnight is the start of the first interval), and SAS then counts the intervals from that point. In some cases, the start of intervals are very obvious. For example, the start of the MONTH interval that includes 4/12/2013 is 4/1/2013. Other are more difficult, like determining the start of the DAY50 interval that includes 12/1/1998? It's 11/17/1998. SAS determines that by counting multiples of 50 days from 1/1/1960. The one exception is for weeks, which always start on a Sunday, so the start of the first week interval is 12/27/1959 (the Sunday of the week that includes 1/1/1960).

Question 39

Describe the INTCK function

Answer 39

Returns the number of intervals between the two values given. For example INTCK('MONTH','13apr2013','5jun2013') equals 2. The dates are 2 MONTH intervals apart.

Question 40

Describe the INTNX function

Answer 40

Advances the value given by a given multiple of an interval. For example, INTNX('MONTH','13apr2013',2) equals 6/1/2013, as that is the start of the interval 2 months from the start of the interval that includes 4/13/2013.