Global Usage
Which Countries Use
24-Hour Time?
The short answer: most of them. The 24-hour clock is the global default, used officially by the majority of the world's nations. The 12-hour AM/PM system is a regional exception, primarily associated with the United States and a handful of other countries.
Countries using 24-hour
Countries where 12-hour dominates daily life
Of militaries worldwide use 24-hour time
Important context: "Using 24-hour time" exists on a spectrum. Many countries use 24-hour time in all official contexts (timetables, government documents, broadcasts) while their populations also use 12-hour colloquially. For this breakdown, we focus on dominant everyday usage and official standard practice.
Regional Breakdown
Europe
24-hourNear-universal 24-hour usage in official contexts. Many countries use 12-hour colloquially but all official timetables are 24-hour.
Asia
24-hourPredominantly 24-hour in formal and official use. Japan and Korea use both systems depending on context.
Africa
24-hourLargely 24-hour in official usage, inherited from European colonial administrative systems and retained for clarity.
Latin America
24-hourOfficial timetables, government, and media use 24-hour time. Mexico straddles both due to US cultural influence.
Oceania
mixedAustralia and New Zealand officially use 24-hour time but 12-hour AM/PM is dominant in everyday speech.
North America
12-hour dominantUS is one of the few countries where 12-hour time dominates everyday use. Canada uses both. Military, aviation, and healthcare use 24-hour.
Other 12-hour
12-hour dominantThese countries use 12-hour time colloquially, though official documents and transportation often use 24-hour.
The Exception
Why Does the US Still Use AM/PM?
The United States is the most prominent holdout for 12-hour timekeeping in everyday life. This is a historical accident more than a deliberate choice. The US was isolated enough from European trade and rail networks during the 19th century that it never felt the strong pressure to standardize that forced most European nations toward 24-hour time.
European railroad networks — which crossed national borders and required passengers from multiple countries to read timetables — adopted 24-hour time early and comprehensively. The US railroad system, domestic and vast, never had that cross-border pressure and kept the familiar 12-hour format that clock faces displayed.
Even within the US, critical industries have shifted entirely to 24-hour time:
US Military
Has used 24-hour time since the Army adopted it in 1942.
Aviation (FAA)
All flight operations use Zulu (UTC) 24-hour time.
Hospitals
Medical charting and medication schedules use 24-hour notation.
Emergency Services
Police, fire, and EMS dispatch use 24-hour time for all logs.
The Trend
The World Is Moving Toward 24-Hour Time
Even in countries that colloquially use 12-hour time, the digital shift is accelerating 24-hour adoption. Smartphones, digital watches, international travel, streaming services with global release times, and online gaming (where players coordinate across time zones) are all pushing younger generations toward comfort with 24-hour notation.
International business communication, logistics software, and programming (where timestamps are nearly always 24-hour) further normalizes the format. ISO 8601, the international standard for date and time representation, mandates 24-hour notation — and any software that handles timestamps internally uses it.
The question is not whether 24-hour time will become universal — it's already the default for the world's systems. The question is only how long colloquial AM/PM usage will persist in the handful of countries where it remains dominant today.
Did You Know
Fun Facts About Time Format Preferences
Japan uses both simultaneously. Train schedules use 24-hour time, but consumer products (alarm clocks, phones in default mode) often show 12-hour. The same person may switch systems multiple times per day.
Some countries go past 24:00. Japan and a few other countries use times like 25:00 or 26:30 to indicate hours past midnight within the same "broadcast day" — a convention used in TV scheduling to avoid crossing the midnight boundary.
The Philippines uses 12-hour colloquially. Despite being a former US territory, formal Philippine documents and the Philippine military use 24-hour time — creating a split between official and everyday usage.
India uses both. Indian Railways (the world's 4th largest railway network, carrying 23 million passengers daily) uses 24-hour time exclusively. Colloquial speech uses 12-hour with "morning," "afternoon," "evening" qualifiers.
Australia's official standard is 24-hour. Despite widespread colloquial 12-hour usage, AS ISO 8601 (the Australian standard) mandates 24-hour representation for all official documentation.
The Internet runs on Zulu time. All internet protocols, server logs, SSL certificates, and international standards use UTC 24-hour time. Every webpage you visit is timestamped in 24-hour format.