Google-sheets – How to set auto update period manually for a Google Spreadsheets published to the web

I believe that the only way to achieve this is to set a locale in which this date format is a default one. For example I have it as default because I have Polish locale.

Link to settings: https://drive.google.com/settings

I've been struggling with the same problem. Instead of writing a custom function, I add a different query string to spreadsheet_url in IMPORTRANGE in the hope that each time the page is refreshed, Google thinks it needs to fetch data from a new spreadsheet. I simply append a new timestamp to make the url unique each time. It's a blatant hack, but it has been working for me across a lot of sheets.

My formula previously looked something like:

=IMPORTRANGE("https://docs.google.com/spreadsheets/d/123123123123/edit#gid=1816927174","'Sheet1'!A1:B25")

And now it looks like:

=IMPORTRANGE("https://docs.google.com/spreadsheets/d/123123123123/edit#gid=1816927174"&"?"&now(),"'Sheet1'!A1:B25")

Update:

This method no longer works since Google no longer permits now() inside importrange(). See comment from Hugh below.