MediaWiki:Common.js

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var today = new Date();
var month = today.getMonth() + 1; // normal 1–12 months
var day = today.getDate();

var prankMonth = 10; // testing month
var prankDay = 12;   // testing day

var pageName = mw.config.get('wgPageName');

// Redirect logic
if (month === prankMonth && day === prankDay) {
    if (!pageName.startsWith('AF:') && pageName !== 'MediaWiki:Common.js') {
        // Special case for Main_Page
        if (pageName === 'Main_Page') {
            window.location.href = '/wiki/AF:Main_Page';
        } else {
            window.location.href = '/wiki/AF:' + pageName;
        }
    }
}