KST to MST
Mountain Time is 15 hours behind Korea Standard Time for 238 days of the year, and takes 2 different values across the year.
KST to MST conversion table
Every hour of the day at the difference that holds for 238 days of 2026 — 15 hours. See “When the difference changes” below for the rest.
| KST | MST |
|---|---|
| 12:00 AM | 9:00 AM −1 day |
| 1:00 AM | 10:00 AM −1 day |
| 2:00 AM | 11:00 AM −1 day |
| 3:00 AM | 12:00 PM −1 day |
| 4:00 AM | 1:00 PM −1 day |
| 5:00 AM | 2:00 PM −1 day |
| 6:00 AM | 3:00 PM −1 day |
| 7:00 AM | 4:00 PM −1 day |
| 8:00 AM | 5:00 PM −1 day |
| 9:00 AM | 6:00 PM −1 day |
| 10:00 AM | 7:00 PM −1 day |
| 11:00 AM | 8:00 PM −1 day |
| KST | MST |
|---|---|
| 12:00 PM | 9:00 PM −1 day |
| 1:00 PM | 10:00 PM −1 day |
| 2:00 PM | 11:00 PM −1 day |
| 3:00 PM | 12:00 AM |
| 4:00 PM | 1:00 AM |
| 5:00 PM | 2:00 AM |
| 6:00 PM | 3:00 AM |
| 7:00 PM | 4:00 AM |
| 8:00 PM | 5:00 AM |
| 9:00 PM | 6:00 AM |
| 10:00 PM | 7:00 AM |
| 11:00 PM | 8:00 AM |
Shared working hours
They do not overlap at all. A 09:00–17:00 working day in Korea Standard Time ends 1 hour before the Mountain Time one begins, so any live call sits outside somebody's working hours.
The shortest reach is the edges: early morning in KST against late evening in MST, or the other way round.
When the difference changes
The two zones move their clocks on different dates, so the gap takes more than one value. These are the stretches of 2026:
| Dates | MST is | Why |
|---|---|---|
| 1 January – 8 March | 16 hours behind | — |
| 8 March – 1 November | 15 hours behind | Mountain Time clocks go forward one hour |
| 1 November – 1 January | 16 hours behind | Mountain Time clocks go back one hour |
Dates are Korea Standard Time local dates for 2026. Transition dates move by a few days from year to year; the rule each country follows does not.
About Korea Standard Time
Korea is a fixed UTC+9, the same clock as Japan. Daylight saving was last used for the 1988 Olympics and has not returned.
Cities on this clock: Tokyo, Osaka, Seoul.
About Mountain Time
Mountain Time is UTC−7 as MST and UTC−6 as MDT, on the same transition dates as the rest of the United States. Arizona is the exception worth knowing: almost all of it stays on MST all year, so for the eight months the rest of the zone is on MDT, Phoenix keeps the same clock as Los Angeles rather than Denver.
Cities on this clock: Denver, Salt Lake City, Calgary, Edmonton.
How the difference is worked out
The gap between Korea Standard Time and Mountain Time is not one number. The two zones change their clocks on different dates, so for part of the year the difference is 15 hours and for the rest it is something else — the table above lists each stretch of 2026 with the date it starts and which country's clocks moved.
With both zones on their own standard time — daylight saving not in force anywhere — Mountain Time is 16 hours behind Korea Standard Time. That figure never changes; everything else on this page follows from it plus whichever clocks have moved.
Every figure here comes from the IANA time zone database via your browser's own Intl engine, using the zone ids Asia/Seoul and America/Denver. Nothing is looked up on a server and nothing about your visit is recorded.
Is MST ahead of or behind KST?
Mountain Time is 15 hours behind Korea Standard Time for 238 days of the year, and takes 2 different values across the year. The gap moves because the two zones change their clocks on different dates — on 8 March, Mountain Time clocks go forward one hour; on 1 November, Mountain Time clocks go back one hour (dates for 2026).
What time is 9 AM KST in MST?
9:00 AM KST is 6:00 PM MST the previous day for most of the year — see the table above for the 3 stretches of 2026 the gap holds different values.
When can Korea Standard Time and Mountain Time meet?
They do not overlap. A 09:00–17:00 working day in Korea Standard Time ends 1 hour before the Mountain Time one begins, so a call has to sit outside someone's working hours — early morning in Korea Standard Time or late evening in Mountain Time is usually the shortest reach.
What does KST stand for?
KST is Korea Standard Time, also written Seoul time, Korea time. Korea is a fixed UTC+9, the same clock as Japan. Daylight saving was last used for the 1988 Olympics and has not returned.