Zulu Time

Zulu time is the military and aviation designation for Coordinated Universal Time (UTC). The name Zulu comes from the old NATO military time zone system. Each zone was assigned a letter and the zero meridian at Greenwich was assigned the letter “Z”. In the phenetic alphabet, letter “Z” is pronounced Zulu. Aviation adopted Zulu time globally for flight plans, weather reports and air traffic communications to avoid confusion from crossing time zones and daylight saving shifts. Ham radio operators also have adopted Zulu time so contacts, contests, and propogation data stay consistent regardless of where each station is physically located.

Every time on this website is written in Zulu time, with some supplemental affordances for your local time.

Reading a time here

You will see Zulu written a few ways, each chosen for where it appears:

• 18:30Z in sentences and on plan cards: hours and minutes with a colon, the reading voice.
• 1745z in dense rows, like an op card’s timeline facts or a logbook column. This is the compact form that hams often write on a paper log.
• 0127:49z in packet logs and expanded contacts, where APRS frames arrive seconds apart and the minute alone cannot order them. The colon marks off the seconds and keeps the familiar 0127z intact. We deliberately do not write 012749z. In raw APRS frames, six digits before a z is how the timestamp is represented in a position report, where those six digits represent day-hour minute (DDHHMMz).
• Dates show the month as an word abbreviation (2 Aug 2026), not a number. This avoids potential confusion about the various numeric only date formats used around the world.

Your local time

Wherever a time in the compact form (2215z) appears, hover over it to see the equivilent time in your local time zone, or tap it and the local time pops up beside it. This local time zone conversion happens in your browser, because the website doesn’t know where you are. One implication is that if the time is wrong on your local computer, the displayed local time will also be wrong.

Plan cards do the translation for you. A planned op’s start is shown in both clocks at once, Zulu on top and your local time under it, each with its own date. Zulu rolls to tomorrow during your evening if you live west of Greenwich, and a plan for 0230z Saturday may well be your Friday night. When the two dates disagree, both are marked in green.

The now page carries a station clock, Zulu beside your local time with ticking seconds.

Why not show everything in local time?

Because the game is shared. An op on the air “until 2130z” ends at one moment. When translated into every reader’s local clock it becomes many different statements that no two people can compare. Ham logging convention settled this decades ago, and we follow it. Log your times in Zulu, making one clock for everyone. Operators convert to their local time as necessary.