How to Check World Time Differences: Calculating the Time Gap with Japan and Daylight Saving Pitfalls

How time differences are determined

Time around the world is expressed as an offset from a reference called UTC (Coordinated Universal Time). Japan Standard Time (JST) is UTC+9, meaning Japan time is UTC plus nine hours. New York’s standard time is UTC−5, so it is UTC minus five hours.

The time difference between two places is simply one offset minus the other. For Japan (+9) and New York (−5), −5 − (+9) = −14: New York is 14 hours behind Japan. When it is 9 a.m. Friday in Japan, it is still 7 p.m. Thursday in New York.

Note that time differences aren’t always whole hours. India is UTC+5:30, 3.5 hours behind Japan, and Nepal is UTC+5:45, on a 15-minute step. If you remember the difference rounded to the hour, you will be 30 minutes late for the meeting.

Steps to check current times and time differences at a glance

Doing the math by hand, you will get daylight saving time wrong. A list that works backward from the current time shows the time difference in effect at that very moment.

1. 1

   Open the world time zones page

   The current times in 13 major countries appear on cards with flags. The date is shown as well, so you can tell at a glance whether a place has crossed into another day.

2. 2

   Find the card for the other person’s country

   The badge at the top right of each card is the time difference from Japan (JST). “−14h vs. JST” means 14 hours behind Japan, and “+1h vs. JST” means one hour ahead. Countries on the same time show “Same as JST.”

3. 3

   Read the current time and date together

   The date and day of the week appear below the time. The bigger the difference, the easier it is to look only at the time and get the date wrong. Check the day of the week before you plan.

4. 4

   Convert the meeting time into their local time

   Think in terms of “what time it will be for them,” not “what time to set in Japan.” Add the number on the badge to Japan time to get their local time.

Quick reference: time differences between major countries and Japan

Time differences relative to Japan (UTC+9). For countries with daylight saving time, the gap shrinks by one hour while it is in effect.

The United States and Canada have time differences within the country. On the US West Coast (Los Angeles), it is three hours earlier than the East, so the gap with Japan is −17 hours (−16 hours during daylight saving time). Don’t lump it together as “US time”; always check by city.

How daylight saving time shifts things by an hour

The most common cause of time-difference mistakes is daylight saving time (DST, or summer time). Europe and North America still move their clocks forward an hour during the months with long daylight hours. Moving clocks forward means the gap with Japan shrinks by one hour for that period.

• Europe: starts on the last Sunday in March and ends on the last Sunday in October. London goes from −9h to −8h, Paris and Berlin from −8h to −7h
• North America: starts on the second Sunday in March and ends on the first Sunday in November. New York goes from −14h to −13h
• Southern Hemisphere: the seasons are reversed, so Sydney observes daylight saving time from early October to early April. The gap with Japan goes from +1h to +2h
• Countries without it: Japan, South Korea, China, India, Singapore, the UAE, Russia and others. Russia moved to permanent standard (winter) time in 2014

The tricky part is that the switch dates differ by country. For about two weeks in mid-March, only North America is on daylight saving time, creating a period when the differences are unlike usual. The “I set it at the same time as last month and they didn’t show up” problem almost always happens during this period.

When checking the time difference pays off

• Online meetings abroad: confirm in their local time that the meeting falls within their working hours
• Booking international flights: arrival times are shown in local time, so they don’t match your sense of flight time. Add or subtract the time difference to see the real travel time
• Overseas online shops and support desks: business hours and shipping cutoffs are in local time. A slow reply often just means it is the middle of the night for them
• Overseas livestreams and ticket sales: unless you convert the on-sale time to your own time, it may be sold out by the time you notice
• Calling family and friends: check they aren’t asleep before you call

When dealing with several people abroad from Japan, mornings in Japan suit Asia and Oceania, evenings suit Europe, and early mornings or late nights suit North America. Often there is no time when everyone is awake, so offering two or three options and letting the others choose gets things scheduled faster.

FAQ

What is the time difference between Japan and the US?

The US has several time zones, so it depends on the city. New York in the East is −14 hours in standard time (−13 hours in daylight saving time), and Los Angeles in the West is −17 hours (−16 hours in daylight saving time). Rather than saying “the US,” check the city where the other person is.

Do I need to shift the calculation by an hour myself during daylight saving time?

The differences shown in the list are calculated from the time zone settings at that moment, so during daylight saving time the figure already reflects it. There is no need to add or subtract an hour by hand. If you calculate from a difference you memorized, on the other hand, you will be off during daylight saving time.

Why do some countries have time differences in half hours?

Because time zones are set not only by longitude but by each country’s own circumstances. India (UTC+5:30) keeps the whole of its large territory on a single time, and the half-hour offset is the compromise. Some places, like Nepal at UTC+5:45, even use a 15-minute step.

Which countries are ahead of Japan?

Japan is at UTC+9, on the early side of the world, so not many countries are ahead. They include eastern Australia (UTC+10, +11 in daylight saving time) and New Zealand (UTC+12). In the list, countries with a plus difference are ahead of Japan.

How should I write the time when sending an invitation for an international meeting?

The safest way is to write both your time and theirs with time zone abbreviations (e.g. March 20, 14:00 JST / 01:00 EDT). If the date changes, include their date too. Calendar invitations automatically convert the time to local time on the recipient’s device.