# Teradata Tutorial – DateTime Related Functions and Examples

This post summarize the common functions that are used when dealing with DateTime datatypes in Teradata.

### Converting String to DateTime

#### String to Date

SELECT CAST('2017-10-15' AS DATE FORMAT 'YYYY-MM-DD');
SELECT CAST('2017 10 15' AS DATE FORMAT 'YYYYBMMBDD');
SELECT CAST('2017 Oct 15' AS DATE FORMAT 'YYYYBMMMBDD');
SELECT CAST('15, Oct, 2017' AS DATE FORMAT 'DD,BMMM,BYYYY');
-- default ansi format
SELECT CAST('2017-10-15' AS DATE);
-- use to_date function
SELECT to_date('2017-10-15', 'YYYY-MM-DD');

#### String to Time

-- no seconds
SELECT CAST('16h20m' AS TIME(0) FORMAT 'HHhMIm');
-- with seconds and space
SELECT CAST('16h 20m 32s' AS TIME(0) FORMAT 'HHhBMImBSSs');
-- with miliseconds
SELECT CAST('16:20:32.2456 ' AS TIME(6));
-- With PM or AM
SELECT CAST('PM 04:20:32.245 ' AS TIME FORMAT 'TBHH:MI:SS.S(4)B');
SELECT CAST('AM 04:20:32.245 ' AS TIME FORMAT 'TBHH:MI:SS.S(4)B');

#### String to Timestamp

SELECT CAST('2017-10-15 23:59:59.999999' AS TIMESTAMP(6) WITH TIME ZONE);
-- with time zone Z
SELECT CAST('2017-10-15 23:59:59.999999 +10:00' AS TIMESTAMP(6) WITH TIME ZONE FORMAT 'YYYY-MM-DDBHH:MI:SS.S(6)BZ');
-- time zone in the string
SELECT CAST('2017-10-15 23:59:59 +10:00' AS TIMESTAMP(0) FORMAT 'Y4-MM-DDBHH:MI:SS.S(6)BZ');

#### String to Interval

SELECT CAST('-114-25' AS INTERVAL YEAR(4) TO MONTH);
SELECT CAST('-9999-11' AS INTERVAL YEAR(4) TO MONTH);
SELECT CAST('9999-11' AS INTERVAL YEAR(4) TO MONTH);

### Converting DateTime to String

#### Conversions

-- using cast
SELECT CAST(CURRENT_TIMESTAMP AS VARCHAR(100));
SELECT CAST(CURRENT_DATE AS VARCHAR(100));
-- using functions
SELECT to_char(CURRENT_DATE,'YYYY-MM-DD');
SELECT to_char(CURRENT_TIMESTAMP,'MON-DD-YYYY" "HH:MI:SS" "TZH:TZM');
-- time examples
SELECT CAST(TIME AS VARCHAR(100));
SELECT CAST(CURRENT_TIME AS VARCHAR(100));
SELECT to_char(CURRENT_TIME,'HH:MI:SS" "TZH:TZM');

#### Extract Components

SELECT EXTRACT(YEAR
FROM CURRENT_TIMESTAMP);
SELECT EXTRACT(MONTH
FROM CURRENT_TIMESTAMP);
SELECT EXTRACT(DAY
FROM CURRENT_TIMESTAMP);
SELECT EXTRACT(MINUTE
FROM TIME);
SELECT EXTRACT(HOUR
FROM TIME);
SELECT EXTRACT(SECOND
FROM TIME);

-- extract from interval
SELECT EXTRACT(DAY
FROM CAST('99' AS INTERVAL DAY(2)));

### DateTime Comparison and Operations

-- add 10 year and 1 month to the current timestamp
SELECT CURRENT_TIMESTAMP + CAST('10-01' AS INTERVAL YEAR(2) TO MONTH);
-- minus 10 years from the current date
SELECT DATE + CAST('-10-00' AS INTERVAL YEAR(2) TO MONTH);

#### DateTime Comparison

-- Timestamp minus timestamp get one interval
SELECT CURRENT_TIMESTAMP - ADD_MONTHS(CURRENT_TIMESTAMP, -133) YEAR(4) TO MONTH;
SELECT DATE - (DATE + CAST('99' AS INTERVAL DAY(2))) YEAR(4) TO MONTH;

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