PostgreSQL TO_DATE() Function: Convert String to Date

Summary: in this tutorial, you will learn how to use the PostgreSQL TO_DATE() function to convert a string to a date.

Introduction to the PostgreSQL TO_DATE() function

The TO_DATE() function converts a string literal to a date value.

Here’s the basic syntax of the TO_DATE() function:

TO_DATE(text,format);

The TO_DATE() function accepts two string arguments.

text: is an input string that you want to convert to a date.
format: specifies the format of the input string.

The TO_DATE() function returns a DATE value.

See the following example:

SELECT TO_DATE('20170103','YYYYMMDD');

Output:

TO_DATE
------------
 2017-01-03

In this example, the string 20170103 is converted into a date based on the input format YYYYMMDD.

YYYY: year in four digits format.
MM: month in two digits format.
DD: day in two digits format.

As a result, the function returns January 3rd 2017.

The following table illustrates the template patterns for formatting date values:

Pattern	Description
Y,YYY	year in 4 digits with comma
YYYY	year in 4 digits
YYY	last 2 digits of the year
YY	The last digit of the year
Y	The last 3 digits of ISO 8601 week-numbering year
IYYY	ISO 8601 week-numbering year (4 or more digits)
IYY	The last 2 digits of ISO 8601 week-numbering year
IY	The last digit of ISO 8601 week-numbering year
I	Abbreviated capitalized month name e.g., Jan, Feb, etc.
BC, bc, AD or ad	Era indicator without periods
B.C., b.c., A.D. ora.d.	Era indicator with periods
MONTH	English month name in uppercase
Month	Full capitalized English month name
month	Full lowercase English month name
MON	Abbreviated uppercase month name e.g., JAN, FEB, etc.
Mon	Week number of the year (1-53) (the first week starts on the first day of the year)
mon	Abbreviated lowercase month name e.g., Jan, Feb, etc.
MM	month number from 01 to 12
DAY	Full uppercase day name
Day	Full capitalized day name
day	Full lowercase day name
DY	Abbreviated uppercase day name
Dy	Abbreviated capitalized day name
dy	Abbreviated lowercase day name
DDD	Day of year (001-366)
IDDD	Day of ISO 8601 week-numbering year (001-371; day 1 of the year is Monday of the first ISO week)
DD	Day of month (01-31)
D	Day of the week, Sunday (1) to Saturday (7)
ID	ISO 8601 day of the week, Monday (1) to Sunday (7)
W	Week of month (1-5) (the first week starts on the first day of the month)
WW	Century e.g., 21, 22, etc.
IW	Week number of ISO 8601 week-numbering year (01-53; the first Thursday of the year is in week 1)
CC	Century e.g, 21, 22, etc.
J	Julian Day (integer days since November 24, 4714 BC at midnight UTC)
RM	Month in uppercase Roman numerals (I-XII; I=January)
rm	Month in lowercase Roman numerals (i-xii; i=January)

PostgreSQL TO_DATE function examples

The following statement converts the string 10 Feb 2017 into a date value:

SELECT TO_DATE('10 Feb 2017', 'DD Mon YYYY');

The output is:

TO_DATE
------------
 2017-02-10
(1 row)

Suppose you want to convert the string 2017 Feb 10 to a date value, you can apply the pattern YYYY Mon DD as follows:

SELECT TO_DATE('2017 Feb 20','YYYY Mon DD');

The function returns the following output:

TO_DATE
------------
 2017-02-20
(1 row)

PostgreSQL TO_DATE() function gotchas

If you pass an invalid date string, the TO_DATE() function will try to convert it to a valid date and issue an error if it cannot. For example:

SELECT TO_DATE('2017/02/30', 'YYYY/MM/DD');

PostgreSQL issued the following error:

ERROR:  date/time field value out of range: "2017/02/30"
LINE 1: SELECT '2017/02/30'::date;

Summary

Use the PostgreSQL TO_DATE() function to convert a string literal to a date value.