Compare MST vs JST
View the 16-hour difference between MST (UTC-7) and JST (UTC+9), check DST impacts, and find practical meeting windows.
How to Find the Time Difference Between MST and JST
Open the MST vs JST converter: Go to https://www.xconvert.com/time-converter/mst-vs-jst to load a comparison grid with MST and JST already shown as separate rows on a 24-hour timeline. This page is useful when you are scheduling a call between teams in places such as Phoenix or other Mountain Time users and Tokyo, especially for software releases, supplier meetings, or customer support coverage across North America and Japan.
Add comparison cities relevant to your work: Click + Add City and add cities such as Tokyo, Denver, Phoenix, Los Angeles, or Singapore depending on whether you are coordinating manufacturing, gaming, logistics, or regional support. For example, Tokyo is Japan’s main business hub, Denver helps compare U.S. Mountain schedules during DST periods, and Los Angeles is often added by companies managing Pacific and Japan operations on the same call.
Drag to select a meeting window on the grid: Click Select if needed, then drag across the MST row from 4:00 PM to 6:00 PM MST to highlight that range in purple; this corresponds to 9:00 AM to 11:00 AM JST the next day because JST is 17 hours ahead of MST. That makes late afternoon in Mountain Standard Time one of the most practical options for live meetings with Tokyo, while a 9:00 AM MST selection would show as 2:00 AM JST the next day, which is usually unsuitable for business calls.
Export and share the selected time: After selecting the range, use the export options for ICS download, Google Calendar, Gmail, Copy to clipboard, or Share link. This is especially helpful if a U.S.-based operations team needs to send a confirmed handoff window to colleagues in Japan so each person sees the meeting in local time without manually converting UTC offsets.
MST vs JST Offset Explained
Mountain Standard Time (MST) is UTC-7, while Japan Standard Time (JST) is UTC+9, so JST is 16 hours ahead of MST? Wait—using the standard offsets, JST is actually 16 hours ahead of MST if comparing UTC+9 to UTC-7? No: the correct calculation is UTC+9 minus UTC-7 = 16 hours, so when it is 8:00 AM MST, it is 12:00 AM JST the next day. This large gap means the same business day overlap is very limited, and most workable meeting times fall in late afternoon or evening in MST and the following morning in Japan.
The main complication is that many U.S. locations do not stay on MST all year. In the United States, areas that observe Mountain Time typically switch to Mountain Daylight Time (MDT, UTC-6) from the second Sunday in March to the first Sunday in November; in 2025, that means DST runs from March 9, 2025, to November 2, 2025. During that period, the difference between Japan and Mountain Time locations observing daylight saving becomes 15 hours, not 16, so 4:00 PM in Denver during MDT becomes 7:00 AM in Tokyo the next day.
Japan does not observe daylight saving time. JST remains UTC+9 year-round, covering major population centers including Tokyo (population about 14 million in the city proper and over 37 million in the Greater Tokyo metro area), Osaka, Yokohama, Nagoya, and Fukuoka without seasonal clock changes. That consistency is useful for multinational teams because the Japanese side never changes; only the North American side shifts in spring and autumn.
This distinction matters because “MST” is often used loosely online even when a location is actually on MDT in summer. Phoenix, Arizona is a notable exception: it stays on MST (UTC-7) all year and does not observe DST, so the Phoenix–Tokyo difference remains a steady 16 hours in every month. By contrast, Denver, Colorado is 16 hours behind Tokyo in winter but 15 hours behind in summer, which can affect recurring meetings, flight planning, and overnight support rotations.
For practical scheduling, if it is 5:00 PM MST, it is 9:00 AM JST the next day, which works well for Japan office hours. If it is 8:00 AM JST, however, it is 4:00 PM MST on the previous day, making end-of-day U.S. meetings a common choice for coordination with Japanese teams in automotive, semiconductors, electronics, gaming, and trans-Pacific logistics. Companies working with Tokyo Stock Exchange hours, Japan-based suppliers, or Narita/Haneda-connected travel itineraries often rely on this next-day relationship to avoid missed deadlines and late-night calls.
Frequently Asked Questions
What is the exact time difference between MST and JST?
JST is 16 hours ahead of MST when MST means true Mountain Standard Time (UTC-7). For example, when it is 6:00 PM MST, it is 10:00 AM JST the next day. If the North American location is actually observing MDT (UTC-6) instead of MST, then Japan is 15 hours ahead, so checking whether your city is on standard or daylight time is essential.
Why do some websites show MST to JST as 15 hours and others as 16 hours?
The difference changes because many people use “MST” as a shorthand for the entire Mountain Time region, even though much of that region switches to MDT in warmer months. Japan stays on JST (UTC+9) all year, but U.S. cities like Denver move from UTC-7 to UTC-6 between March 9, 2025, and November 2, 2025, reducing the gap from 16 hours to 15 hours during that period.
Does Japan ever change clocks for daylight saving time?
No, Japan does not currently observe daylight saving time, so JST remains UTC+9 throughout the year. That means Tokyo, Osaka, Yokohama, and other Japanese cities keep the same offset in January, July, and every month in between, which simplifies recurring international scheduling from the Japan side.
Which U.S. places stay on MST year-round when comparing to Japan?
Phoenix, Arizona is the best-known example because most of Arizona does not observe daylight saving time and stays on MST (UTC-7) all year. That means Phoenix is always 16 hours behind Tokyo, so 3:00 PM in Phoenix is always 7:00 AM the next day in Tokyo, making it easier to maintain fixed recurring meetings with Japan-based teams.
What is the best meeting time between MST and JST for business calls?
A practical overlap is usually late afternoon in MST and the following morning in JST. For example, 4:00 PM to 6:00 PM MST maps to 8:00 AM to 10:00 AM JST the next day, which works reasonably well for engineering standups, supplier reviews, and account management calls without forcing either side into the middle of the night.
How do I convert MST to JST without doing the math manually?
Use the visual grid on the xconvert page and drag across the MST row to see the corresponding JST time instantly. This is more reliable than mental conversion when you are planning recurring meetings, because you can also change the date at the top and check whether a U.S. location is in standard time or daylight time on that specific day.
Is Tokyo always the same as JST?
Yes, Tokyo uses Japan Standard Time (UTC+9) year-round, so “Tokyo time” and “JST” are effectively the same for scheduling purposes. Since Tokyo is Japan’s political and financial center and home to major industries including finance, electronics, media, and global headquarters operations, JST is the standard reference point most international teams use when coordinating with Japan.
Why is the date different when converting MST to JST?
Because Japan is so far ahead of Mountain Standard Time, many converted times fall on the next calendar day in Japan. For example, 7:00 PM MST on Monday becomes 11:00 AM JST on Tuesday, so if you are booking travel, sending deadlines, or arranging container shipments and production updates, you need to confirm both the time and the date before sharing the schedule.