Is Noon "12 a.m." or "0 p.m." in Japanese? A Conversion Table Between a.m./p.m. and the 24-Hour Clock

The short answer: "12 a.m." and "0 p.m." are the same moment at noon

In Japanese, noon (12 o'clock midday) can be written either as gozen 12-ji (12 a.m.) or gogo 0-ji (0 p.m.), and both mean the same moment. Likewise, midnight can be written gozen 0-ji (0 a.m.) or, from the previous day's point of view, gogo 12-ji (12 p.m.). It isn't that one of them is strictly correct; the confusion comes from there being two ways of thinking about it.

In Japan today, TV and radio listings and the like commonly use gogo 0-ji and gozen 0-ji, counting both a.m. and p.m. from 0 to 11. On the other hand, writing noon as gozen 12-ji also has the historical basis described next.

The timekeeping rules set in the Meiji era

Japan began using a.m. and p.m. with two sets of 12 hours when it decided to switch to the solar (Gregorian) calendar in Meiji 5 (1872). The proclamation announcing the calendar reform came with a table of hours, listing a.m. from "zero o'clock" to "twelve o'clock" and p.m. from "one o'clock" to "twelve o'clock".

• In this table, noon is written as "twelve o'clock a.m.".
• Midnight (12 o'clock at night) is written as "twelve o'clock p.m.".
• The form "zero o'clock p.m." (gogo 0-ji) does not appear in the table.

So following the Meiji-era rule, noon = 12 a.m. However, writing times in the 12 o'clock hour this way, such as "12:30 a.m.", makes them hard to tell apart from times in the a.m. 0 o'clock hour. In practice, then, treating the hour from noon to 1 o'clock as the "0 p.m. hour" spread, and today both forms are in use.

Conversion table between a.m./p.m. and the 24-hour clock

To convert from the 24-hour clock to a.m./p.m., times before 12 just get "a.m."; for 12 and later, subtract 12 and add "p.m.". The table below uses the common modern style that writes noon as 0 p.m.

To convert the other way, from a.m./p.m. to the 24-hour clock, add 12 to p.m. times. 3 p.m. is 3 + 12 = 15:00, and 11 p.m. is 23:00. 0 p.m. (noon) becomes 0 + 12 = 12:00.

Which is which: 12 AM and 12 PM in English?

English AM and PM, unlike the Japanese convention, use 12 and never write 0 o'clock. So the handling of the 12 o'clock hour differs from the Japanese gogo 0-ji style.

Even in English-speaking countries, 12 AM and 12 PM are often mixed up, so people frequently write "12 noon" and "12 midnight" or use the 24-hour clock. When giving times across borders, it's also worth checking how to look up time differences around the world.

Writing times that cross midnight without mistakes

Trouble tends to arise when a time is combined with a date. "0 a.m. on 20 October" is the instant the 20th begins, in other words the end of the night of the 19th. If you write it meaning "late at night on the 20th", you'll be a day off.

• Deadlines: writing "by 23:59 on 20 October" or "by 24:00 on 20 October" makes it clear you mean the end of the 20th. Avoid "by 0 a.m. on the 20th", which can be read as the end of the 19th.
• Writing 24:00 and 25:00: shop hours such as "open until 24:00" and TV listings such as "25:00 (1 a.m. the next day)" sometimes continue the day past 24:00.
• Write noon as "noon": writing "12:00 (noon)" gets through to people whichever a.m./p.m. convention they follow.
• Write midnight as "midnight (0:00)": the form gogo 12-ji (12 p.m.) is hardly ever used and is easily misunderstood.
• When in doubt, use the 24-hour clock: in bookings and work messages, writing "12:00" or "0:00" all but eliminates mistakes.

Recommended forms for different situations

When writing noon and midnight, the most important thing is that the other person can't misunderstand. Here are the clearest forms for each situation.

Especially where a date and time go together, as with deadlines and release dates, choosing a form that makes it obvious whether you mean the end of the day or the start of it prevents queries and trouble.

Tips for teaching a.m. and p.m. to children

In Japanese elementary schools, a.m. and p.m. are taught in Grade 2. The hour hand goes round twice a day, so the key is understanding that the same "3 o'clock" can be 3 o'clock in the middle of the night before morning or 3 o'clock snack time in the afternoon.

1. 1

   Draw a number line for the day

   Draw a line from 0:00 to 24:00 and write "noon" at 12 in the middle. The left half is a.m. and the right half is p.m.

2. 2

   Add daily events

   Writing in their own day, such as waking up (7 a.m.), school lunch (around 0:30 p.m.), snack (3 p.m.) and bedtime (9 p.m.), makes it feel real.

3. 3

   Check that the hour hand goes round twice a day

   Turn the hands on a real clock to show that the hour hand goes round once in the morning and once in the afternoon.

4. 4

   Match the school's style

   How noon is written can differ between textbooks. Tell children to answer tests using the form taught in class.

Calculating so many minutes before or after across noon is explained in detail in how to work out times and durations.

Check a.m./p.m. and the 24-hour clock on a clock face

In "Move the clock" in the Clock Reading Practice tool, moving the hands shows the current time in both a.m./p.m. and 24-hour form. Turn the minute hand round several times past 12 and you can watch it switch from a.m. to p.m., and from p.m. to a.m. of the next day. Noon is shown as 0 p.m. and midnight as 0 a.m.

In "Practice quiz", the "Elapsed time" section has a "Crossing noon (AM / PM)" level for practising questions where a.m. and p.m. swap over, such as "What time is 20 minutes after 11:50 a.m.?". The reading guide also includes how to read "0:00 (0 a.m.)", "12:00 (noon)" and "24:00" in Japanese.

FAQ

Is noon correctly 12 a.m. or 0 p.m. in Japanese?

Both refer to the same moment. In the table of hours attached to the 1872 (Meiji 5) calendar reform proclamation, noon is written "twelve o'clock a.m.", but today gogo 0-ji (0 p.m.) is also widely used on TV, radio and elsewhere. To avoid mistakes, writing "noon" or "12:00" is the safest.

What day and time is 0 a.m.?

It is the instant the day begins. "0 a.m. on 20 October" is when the night of the 19th ends and the 20th starts. If you mean the night of the 20th, write "24:00 on 20 October" or "0:00 on 21 October".

What time is 12 p.m. in Japanese?

Under the Meiji-era rule, gogo 12-ji (12 p.m.) means 12 o'clock at night (midnight). However, some people take it to mean noon and misunderstandings are common, so it is hardly used today. For midnight, writing "midnight (0:00)" or "24:00" is recommended.

Is 12 PM midday or midnight?

12 PM is midday (noon) and 12 AM is midnight. English doesn't use 0 o'clock, so the Japanese gogo 0-ji corresponds to 12 PM and gozen 0-ji to 12 AM.

How do I convert the 24-hour clock to a.m./p.m.?

Before 12, just add "a.m."; for 12 and later, subtract 12 and add "p.m.". 15:00 is 3 p.m. and 23:00 is 11 p.m. 12:00 is 0 p.m. (noon) and 0:00 is 0 a.m.