SQL Query to Convert from CST to AEST or AEDT

SQL Query to Convert from CST to AEST or AEDT.sql

SELECT 
    CASE 
        /*  Check if the current date is between the first Sunday of October and the first Sunday of April (AEDT period) */
        WHEN GETDATE() >= 
            /*  First Sunday in October */
            DATEADD(DAY, 1 - DATEPART(WEEKDAY, DATEFROMPARTS(YEAR(GETDATE()), 10, 1)) + 7 * (1), DATEFROMPARTS(YEAR(GETDATE()), 10, 1)) 
            AND GETDATE() < 
            /*  First Sunday in April */
            DATEADD(DAY, 1 - DATEPART(WEEKDAY, DATEFROMPARTS(YEAR(GETDATE()), 4, 1)) + 7 * (1), DATEFROMPARTS(YEAR(GETDATE()), 4, 1))
        THEN DATEADD(HOUR, 17, GETDATE())  /* AEDT (UTC+11) */
        ELSE DATEADD(HOUR, 16, GETDATE())  /*  AEST (UTC+10) */
    END AS LocalDateTime

Explanation:

GETDATE(): This function gets the current date and time from the SQL server (in CST).

First Sunday in October:

DATEFROMPARTS(YEAR(GETDATE()), 10, 1): Generates the date for October 1st of the current year.

DATEPART(WEEKDAY, ...): This function determines which weekday October 1st falls on.

The formula DATEADD(DAY, 1 - DATEPART(WEEKDAY, ...) + 7 * (1), ...) adjusts the date to find the first Sunday in October.

First Sunday in April:

DATEFROMPARTS(YEAR(GETDATE()), 4, 1): Generates the date for April 1st of the current year.

Similar to October, it adjusts the date to find the first Sunday in April.

CASE:

Checks if the current date (GETDATE()) is between the first Sunday of October and the first Sunday of April.

If it is, it adds 17 hours (CST to AEDT).

Otherwise, it adds 16 hours (CST to AEST).

How It Works:
If the current date is between the first Sunday in October and the first Sunday in April, the query adds 17 hours to convert CST (UTC-6) to AEDT (UTC+11).

If the current date is outside that range (i.e., from the first Sunday in April to the first Sunday in October), the query adds 16 hours to convert CST to AEST (UTC+10).

Example:
During AEDT (October to April):

If today is October 5th, 2025, the query will add 17 hours to CST and return the converted time in AEDT (UTC+11).

Outside AEDT (April to October):

If today is July 10th, 2025, the query will add 16 hours to CST and return the converted time in AEST (UTC+10).