TimezoneMask

Choose a timezone. A different zone. The same moment.

TimezoneMask lets you choose the timezone used by supported web pages. Search for a city, IANA timezone or UTC offset, then apply your choice with one click. Useful for checking date and time displays across regions and testing websites with different timezone settings. FEATURES • Search cities, timezone names and offsets such as +8, -10, +5:30 or +5:45. • Browse by region, save favorite zones, or choose a random timezone. • Apply a timezone to all supported websites or only specified websites. Set individual website timezones or exclude a website with system settings. • Optionally change the default webpage locale used by Intl and date/number formatting. This is separate from the extension interface language. • Check the actual Date/Intl timezone, UTC offset, seasonal offsets and locale reported by a selected web page using the built-in checker. • Pause timezone changes and restore the system timezone. Settings are saved locally. • 14 interface languages, light and dark themes, and automatic daylight-saving offsets from IANA zones. HOW TO USE 1. Open a normal HTTP or HTTPS webpage. 2. Open TimezoneMask and search for a timezone. Click a result to apply it. 3. Choose All websites or Only specified websites and add website rules if needed. 4. Use Check timezone to inspect the selected webpage. Refresh the webpage if it previously cached or displayed a time. IMPORTANT LIMITATIONS TimezoneMask uses Chrome's debugger API to change native webpage timezone settings. Chrome displays a debugging notification while it is connected. Opening DevTools, another debugger, or dismissing the notification can interrupt the connection. Select the timezone again to reconnect. Browser-internal pages, extension pages and extension stores are not supported. Early-loading scripts, separate workers and cross-process iframes are not guaranteed to be covered. Explicitly specified website timezones remain unchanged. The extension does not change your computer clock, IP address, location or server time, and is not a complete browser fingerprint protection tool. Changing webpage locale does not translate page text or change navigator.language or request headers. PRIVACY No account, analytics, advertising trackers or remote executable code. Preferences, favorites and website rules stay in local browser storage. Relevant tab URLs, titles and timezone/locale diagnostics are processed locally to apply your rules and show results; they are not sent to the developer or external servers.