SQLite Date & Time - julianday()

In SQLite, you can work with date and time values using various built-in functions. One such function is the julianday() function, which returns the Julian day number for a specifc date and time stamp.

Syntax

The syntax for the julianday() function is as follows:

julianday(date_string, [modifier_1, modifier_2, ...])

• date_string: The date and time string to be converted to a Julian day number. This string can be in any format supported by SQLite, such as YYYY-MM-DD HH:MM:SS.
• modifier_1, modifier_2, ...: An optional list of modifiers to adjust the returned Julian day number. These modifiers can include localtime, utc, and others.

Example

Let's say we want to calculate the Julian day number for the date '2022-01-01'. We can use the julianday() function as follows:

SELECT julianday('2022-01-01');

Output

The output of the above example would be:

2459592.5

Explanation

In the example above, we use the julianday() function to calculate the Julian day number for the date '2022-01-01'. The function returns the Julian day number as a floating point value, which represents the number of days since noon GMT on January 1, 4713 BCE.

Use

The julianday() function can be used to calculate the difference between two dates in days, or to compare dates using their Julian day numbers. It can also be used to perform date arithmetic and to manipulate dates in various other ways.

Important Points

• The julianday() function assumes the Gregorian calendar for dates before October 15, 1582, and the Julian calendar for earlier dates.
• The julianday() function returns the Julian day number as a floating point value. To convert it to an integer value, you can use the CAST() function, as follows:

SELECT CAST(julianday('2022-01-01') AS INTEGER);

• The julianday() function does not handle time zones. To convert a local time to UTC before calculating the Julian day number, use the datetime() function with the utc modifier, as follows:

SELECT julianday(datetime('now', 'utc'));

Summary

In this tutorial, we learned about the julianday() function in SQLite, used to calculate the Julian day number for a given date and time stamp. We saw examples of how to use the function, and discussed its uses and important points. The julianday() function is useful for performing date arithmetic and for manipulating dates in various other ways.