There are three important places where you specify Locale.
- The Google Sheets Locale
- The AppSheet Table Locale
- The mobile device or browser locale
This article primarily explains the first two https://help.appsheet.com/en/articles/961395-locale-support-in-appsheet.
These two setting control how your data is stored and formatted in the Google Sheet. The AppSheet Table Locale must match the Google Sheet Locale because it ensure that Google Sheets and AppSheet reads and writes the Google Sheet data in the correct locale.
The article also mentions the mobile device or browser locale. The mobile device or browser locale completely controls how you data is displayed to the application users. The article contains the following four points regarding the mobile device or browser locale.
4. Make certain that your browser or device is set to use your locale. For example, in the United Kingdom, select the UK locale. In Thailand, select the Thai locale. The browser or device setting completely determines how data values are displayed within the app running on your browser or device.
5. If you use a calendar other than the Gregorian calendar, make certain that your browser or device is set to use that calendar. For example, in Thailand, select the Buddhist calendar. Many countries use the Gregorian calendar, so in many cases you can skip this step.
6. Click the Sync button in the app to read the latest values from the Google Sheet. See if the Date, DateTime, Decimal, Percent, Price, and Time values are displayed correctly in the app. If not, verify your browser or device locale settings.
7. Try updating a Date, DateTime, Decimal, Percent, Price, or Time value and saving the changes to the server. See if the correct values appear in the Google Sheet and the app.
The article also explains that:
All data is sent between the app and the AppSheet server in a common universal format. This makes it easier for the app and server to communicate. It has no effect on how data is stored in the worksheet or displayed in the client.
We refer to this “common universal format” as “wire format” internally, because it is the format used to transmit data between the client and server over the network. “wire format”. The client and server are both capable of converting between localized and wire format. The wire format and the conversions we do internally are all transparent to your application.
Our Locales are based on the Windows Locales. Each Window Locale specifies how dates, times, date/times, currency, decimal, percent, and other values are stored and displayed. We do not support an “en-IN” (English_India) locale because Windows does not support it.
If I understand you question correctly, I think your are asking about choosing the Google Sheets locale. The AppSheet Table Locale always matches the Google Sheets Locale. You should choose the Google Sheets locale that most closely matches how you want to manually enter and view data in your Google Sheet. If you are simply using Google Sheets as a place to store your AppSheet data and you seldom., if ever, enter or view data directly in the Google Sheet browser interface, you could choose any Locale.
The Google Sheets Locale need not match the the mobile device or browser locale specified by your application users. Different users could even specify different locales. The Locale only affects how the data is displayed on the user’s device or browser. The data is sent between the client and server in “common universal format” that is “wire format” The Server reads and writes data to the Google Sheet in the Google Sheets Locale format.