How to update datetime by +15 hours with MySQL

Question

I have a table containing a datetime column.

I need to add 15 hours to all these values.

e.g.

As Is: 2007-08-22 08:55:10  
To Be: 2007-08-22 23:55:10

As Is: 2009-08-22 14:55:10  
To Be: 2009-08-23 05:55:10

Is there a MySQL UPDATE query that can do this?

Answer 1

Given that test is the table, date_col is the column with the date to be updated and id is the primary key of the test table:

update test set date_col = ADDTIME(date_col, '15:0:0') where id=1;

tested with mysql version 5.5.4

Answer 2

update table_name set column_name =DATE_ADD(column_name, INTERVAL 15 HOUR)