Change Outlook Calendar to Military Time

To change Outlook Calendar to military time (24-hour format), open Outlook, go to File > Options > Calendar, and under the “Time zones” section, change the “Time format” from 1:00 PM to 13:00. This setting applies to the calendar views in both Outlook desktop and Outlook on the web, though the exact menu path differs slightly by version.

Why Use Military Time in Outlook?

Military time, also known as 24-hour time, eliminates the ambiguity of AM/PM. It is standard in many professions—healthcare, the military, aviation, and international business—where a misread time can cause missed shifts or double-booked appointments. Outlook lets you switch the calendar to 24-hour format without changing your system clock, so you can keep your computer on 12-hour time but view your schedule in 24-hour time.

How to Change Outlook Desktop (Windows)

In the Outlook desktop app for Windows, the setting is buried in the calendar options. Here is the exact path:

1. Open Outlook and click File in the top-left corner.
2. Click Options at the bottom of the left sidebar.
3. In the Outlook Options dialog, select Calendar from the left list.
4. Scroll down to the Time zones section.
5. Find the Time format drop-down menu. Choose 13:00 instead of 1:00 PM.
6. Click OK to save.

This changes the display in the calendar grid, the scheduling assistant, and the time bar in the day/week/month views. It does not change the time format in emails or the reading pane—those still use your Windows regional settings.

How to Change Outlook on the Web (OWA)

Outlook on the web (the browser version) has a similar setting, but it is under the general settings, not calendar-specific:

1. Click the gear icon (Settings) in the top-right corner.
2. Select View all Outlook settings at the bottom of the panel.
3. Go to General > Language and time.
4. Under Time format, select 13:00 (24-hour).
5. Click Save.

Note that this setting affects all time displays in Outlook on the web, not just the calendar. If you only want the calendar in 24-hour time, you may need to use the desktop app, as the web version does not have a calendar-only time format option.

How to Change Outlook for Mac

Outlook for Mac uses the macOS system settings for time format. To get 24-hour time in the calendar:

1. Close Outlook.
2. Open System Settings (or System Preferences on older macOS).
3. Go to General > Language & Region.
4. Under Time format, select 24-Hour Time.
5. Reopen Outlook. The calendar will now display times in 24-hour format.

This changes the time format for the entire Mac, not just Outlook. There is no separate Outlook-specific setting on Mac.

How to Change Outlook Mobile App

On the Outlook mobile app (iOS and Android), the calendar time format follows the device’s system time setting. To switch to 24-hour time:

• iPhone/iPad: Go to Settings > General > Date & Time, and toggle on 24-Hour Time.
• Android: Go to Settings > System > Date & time, and toggle on Use 24-hour format.

After changing the device setting, reopen Outlook. The calendar will reflect the new format.

Common Problems and Fixes

Sometimes the setting does not take effect immediately. Here are the most common issues:

• Outlook not showing 24-hour time after change: Close and reopen Outlook. If that fails, restart your computer. The setting is cached.
• Calendar still shows AM/PM in meeting invitations: The time format in the calendar grid changes, but the time format in the email body of an invitation is controlled by the email’s formatting, not the calendar setting. Use the calendar grid to confirm the change.
• Outlook on the web ignores the setting: Clear your browser cache or try a different browser. Also, check if you have a group policy that overrides the setting.
• Mac setting does not apply: Ensure you are changing the system time format, not just the calendar format in the menu bar. The setting in System Settings > Language & Region is the one that affects Outlook.

Frequently Asked Questions

Will changing Outlook to military time affect my system clock?

No. In Outlook desktop (Windows) and Outlook on the web, the setting is independent of your Windows or Mac system clock. Your taskbar clock can remain in 12-hour format while Outlook shows 24-hour time. On Mac and mobile, the setting is tied to the system, so changing it will affect the whole device.

Can I have different time formats for different calendars (e.g., work vs. personal)?

No. The time format is a global setting for the Outlook application. It applies to all calendars you have open in that instance. There is no per-calendar time format option.

Does the 24-hour time setting affect meeting times sent to others?

No. The meeting time is stored as a date and time value. Recipients see the time in their own Outlook time format. Changing your display format does not change the actual meeting time or what others see.

How do I revert back to 12-hour time?

Follow the same steps and choose 1:00 PM (or 12:00 on Mac/mobile) instead of 13:00. The change is immediate.

Why does Outlook on the web not have a calendar-specific time format?

Microsoft designed the web version to use a single global time format for consistency across all modules (mail, calendar, contacts). The desktop version has a calendar-specific setting because it integrates more deeply with Windows regional settings.

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