Switch your Mac clock to 24-hour time

The clock-format switch on a Mac isn't where most people look for it — it's tucked under General, not under the menu bar or a "Clock" pane. To change from 12-hour AM/PM to 24-hour, open System Settings → General → Date & Time and turn on 24-hour time. This guide walks you to the exact toggle and shows how to reverse it.

Where the switch actually lives

On older macOS versions this setting sat in a dedicated "Date & Time" preference pane with a "Show 24-hour clock" checkbox on the Clock tab. Since the System Settings redesign in Ventura, it moved — and the tab structure is gone — so it's easy to hunt in the wrong place. Here's the direct path:

1. Open System Settings from the Apple menu.
2. Click General in the sidebar, then Date & Time.
3. Turn on the 24-hour time switch.

The moment you flip it, the menu-bar clock changes format — 1:45 PM becomes 13:45. There's nothing to save and nothing to restart. The path is identical on macOS 13 Ventura, 14 Sonoma, and 15 Sequoia.

Do it from Terminal instead

The switch you just flipped writes a single preference value. You can set the same value directly, which is handy on a Mac you're configuring remotely or via a setup script:

# Switch the menu-bar clock to 24-hour
defaults write com.apple.menuextra.clock Show24Hour -bool true
killall ControlCenter

# Switch back to 12-hour AM/PM
defaults write com.apple.menuextra.clock Show24Hour -bool false
killall ControlCenter

If you'd rather clear the preference entirely and let macOS fall back to its default, run defaults delete com.apple.menuextra.clock Show24Hour followed by killall ControlCenter. The killall step restarts the clock so the new format shows without logging out.

What the switch does and doesn't touch

This one toggle handles the format of the clock in the top-right of your screen — the number of hours, and whether AM/PM appears. A few related things are governed elsewhere, and it's worth knowing which is which so you don't chase the wrong setting:

• Seconds, day of week, the date — those live in the same Date & Time area as separate toggles.
• 24-hour formatting across apps and system strings — that follows System Settings → General → Language & Region → 24-Hour Time. Switch that on too if you want a consistent 24-hour format beyond the corner clock.
• The actual time and zone — set automatically or manually further up the same Date & Time pane; the format switch never changes what time it is, only how it's written.

Because both the clock switch and the region switch are independent and reversible, you can flip either one, glance at the result, and flip it back with no lasting effect.

Tweak the rest of the clock

Once the format is right, you can decide what else the clock shows. See how to show the date in the Mac menu bar to add the day and date next to your new 24-hour time.