Zulu time is Coordinated Universal Time written in military style, with a trailing Z — 1430Z. It exists so that units in different countries can name a single instant without anyone doing time-zone arithmetic. The clock above shows Zulu time live, alongside the zone letter for your own offset, so you can see exactly how far your local clock sits from the reference.
Where the name comes from
Each whole-hour offset from UTC has a letter in the NATO phonetic alphabet. UTC itself is Z, spoken "Zulu". Offsets ahead of UTC take A through M and offsets behind take N through Y — with J deliberately skipped, reserved for whatever the observer's own local time happens to be. That is why you will see 1200Z but never 1200J on an operations order.
When to use Zulu instead of local time
Use Zulu whenever more than one time zone is involved: flight plans, weather reports, incident logs and multinational exercises all run on it. Within a single location, plain military time is enough. Our guide to Zulu time covers the letter system and conversion in detail.