I have copied a script for: when you visit an url, with values in the url: my googlesheet automatically fills with the values hidden in the url in cell and on the same lin
There are two ways for changing the time zone in your Spreadsheet. The first one is through the UI and the second one is programmatically.
Go to File -> Spreadsheet settings, a pop-up window will open as in the next image:
As you can see there's one option to change the time zone to the one you desire.
The Spreadsheet Class has the setSpreadsheetTimeZone(timezone) method, which will change the time zone in the Spreadsheet, but now programmatically. This is a little example of how using it:
function dateFormat() {
var ss = SpreadsheetApp.openById("your-id");
// Get the current Spreadsheet's time zone
var currentTimeZone = ss.getSpreadsheetTimeZone();
Logger.log(currentTimeZone); // Check the current time zone
// Set the new Spreadsheet's time zone
var updatedTimeZone = ss.setSpreadsheetTimeZone("Europe/Paris");
Logger.log(updatedTimeZone); // Check the updated time zone
}