Time zones exist because the Earth is divided into 24 roughly hour-wide bands, each set to a local standard time so clocks roughly match the sun's position. This tool combines a live world clock for a set of major cities with a converter that lets you pick any date and time in one zone and instantly see the matching time everywhere else — handy for scheduling calls, coordinating with remote teams, or knowing when to call family abroad.
Every time is calculated using each time zone's current UTC offset. Many zones observe daylight saving time, so the offset from UTC can change twice a year, which is why this tool always uses live, rule-based time zone data instead of fixed offsets. When you enter a date and time in one zone, the tool converts it to UTC first, then re-expresses that UTC instant in every other zone.