Timezones at a glance
When it's Tuesday 3 PM in Seoul, it's Monday 2 AM in New York. Stop counting on your fingers — compare every city you care about side by side.
Change the base time and every row updates instantly. Five default cities (Seoul · UTC · New York · London · Tokyo) are preloaded; add or remove others freely via search.
How it works
The browser's Intl.DateTimeFormat API queries the IANA timezone database. No extra library to download — every city your operating system knows about (hundreds of them) is searchable. Daylight Saving Time is applied automatically, so March / November transitions are reflected accurately.
UTC offsets render as +9, -5, etc., with half-hour offsets (UTC+9:30 for parts of Australia) handled precisely. Short names (KST · EST · JST) are also shown, ready to paste into emails or calendar invites.
Use cases
Cross-border collaboration — When scheduling a daily meeting, instantly verify that everyone's local time falls within waking hours (typically 9 AM – 6 PM in their region).
Travel itineraries — Record the times of departure / layover / arrival cities side by side to simplify connection waits and hotel check-in math.
International emails — Write "Tuesday 3 PM KST = Monday 11 PM PST" lines instantly, with both timezones explicit, for less ambiguity.
Data handling
The base time and your selected cities are stored only in sessionStorage and disappear when you close the tab. Nothing is uploaded to a server.
Base time · cities never leave the page
Both the base time and your city list are stored only in sessionStorage and disappear when you close the tab. Timezone lookups go through the browser Intl API — zero external traffic.