IRKST — Irkutsk Summer Time
See what IRKST means, when UTC+9 applies, and how to compare or convert it with other time zones worldwide.
How to Convert IRKST to Other Time Zones
Open the IRKST converter page: Go to https://www.xconvert.com/time-converter/irkst-time-zone to open the visual comparison grid with IRKST (Irkutsk Summer Time) pre-loaded as the reference row. This page is useful when you need to line up working hours in eastern Siberia with teams in Asia-Pacific or Europe, such as scheduling a logistics update tied to rail freight, mining operations, or regional government coordination around Irkutsk.
Add comparison cities with the + Add City button: Click + Add City and search for cities such as Tokyo, Seoul, and Singapore to compare IRKST against major East Asian business hubs that often overlap with Russia’s Far East trade, manufacturing, and shipping schedules. You can also add Moscow if you need an internal Russia comparison, because IRKST at UTC+9 is typically 5 hours ahead of Moscow Standard Time (UTC+3), which matters for same-day approvals and handoffs.
Drag across the grid to select a meeting window: Click Select if needed, then drag across the IRKST row to highlight a time block in purple, such as 9:00 AM to 11:00 AM IRKST. That range converts to 9:00 AM to 11:00 AM in Tokyo (JST, UTC+9), 9:00 AM to 11:00 AM in Seoul (KST, UTC+9), and 8:00 AM to 10:00 AM in Singapore (SGT, UTC+8), which quickly shows that a morning call in Irkutsk works well for Northeast Asia but starts earlier for Southeast Asia.
Export and share the selected time range: After selecting a slot, use the export options shown on the page: ICS download, Google Calendar, Gmail, Copy to clipboard, or Share link. For example, you can send an ICS file to a distributed operations team so the meeting appears in each participant’s local time automatically, or use Copy to clipboard to paste a confirmed IRKST-to-Tokyo/Seoul schedule into Slack or email.
About Irkutsk Summer Time (IRKST)
IRKST stands for Irkutsk Summer Time. Its exact offset is UTC+9:00, meaning the local clock is 9 hours ahead of Coordinated Universal Time; when it is 12:00 UTC, it is 21:00 IRKST.
IRKST is the daylight saving version historically associated with the Irkutsk time zone in Russia, centered on the Irkutsk Oblast area in eastern Siberia near Lake Baikal. Irkutsk itself is a major regional center with a population of roughly 600,000+ people, and the wider oblast has about 2.3 million residents, making the time zone relevant for transportation, energy, public administration, and regional commerce.
In practical comparison terms, IRKST (UTC+9) is 1 hour ahead of China Standard Time (UTC+8), the same as Japan Standard Time and Korea Standard Time (UTC+9), and 6 hours ahead of Central European Summer Time (UTC+3). That means when it is 9:00 AM IRKST, it is 8:00 AM in Beijing, 9:00 AM in Tokyo, and 3:00 AM in Berlin during summer, which is important when planning cross-border calls or overnight reporting cycles.
The same UTC+9 offset is also used by abbreviations such as JST, KST, YAKT, WIT, AWDT, CHOST, PWT, TLT, ULAST, and the military zone letter I, but these are not interchangeable in meaning. They refer to different regions or seasonal rules, so using a dedicated IRKST converter avoids confusion when a timestamp specifically references Irkutsk Summer Time.
IRKST and Daylight Saving Time
IRKST is a daylight saving time designation, not a year-round standard time label. It represents the Irkutsk region when clocks are advanced to UTC+9:00, and its standard-time counterpart is Irkutsk Time (IRKT), UTC+8:00.
Historically, regions using Irkutsk Summer Time switched forward from IRKT to IRKST in spring and back from IRKST to IRKT in autumn. Under the former Russian DST pattern, clocks typically moved forward on the last Sunday in March and back on the last Sunday in October, usually at local overnight transition times.
For the current year, 2026, the corresponding DST transition dates would be 29 March 2026 for the move to summer time and 25 October 2026 for the return to standard time if that historical system were in effect. On 29 March 2026, the clock would move from UTC+8 to UTC+9, and on 25 October 2026, it would move back from UTC+9 to UTC+8.
In real-world use, this matters when reviewing older timestamps, archived transport records, legacy software settings, or historical event schedules that still reference IRKST. Russia abolished nationwide seasonal clock changes in 2014, so modern civil time in the Irkutsk region no longer switches between IRKT and IRKST in the old seasonal way, but the abbreviation still appears in historical data and some technical databases.
Frequently Asked Questions
What does IRKST stand for?
IRKST stands for Irkutsk Summer Time. It is the daylight saving time label historically used for the Irkutsk region of Russia when clocks were set to UTC+9:00, one hour ahead of standard Irkutsk Time (IRKT, UTC+8).
Is IRKST the same as GMT?
No, IRKST is not the same as GMT. GMT is effectively UTC+0, while IRKST is UTC+9, so IRKST is 9 hours ahead of GMT; when it is 10:00 AM GMT, it is 7:00 PM IRKST.
Which cities use IRKST?
The abbreviation is associated primarily with Irkutsk and the surrounding Irkutsk region in eastern Siberia. In historical and technical contexts, it may also apply to nearby areas that followed the same Irkutsk seasonal time rules, but the principal city tied to the name is Irkutsk, a major administrative and transport center near Lake Baikal.
What is the UTC offset for IRKST?
The exact UTC offset for IRKST is UTC+9:00. This means local time is 9 hours ahead of UTC, so 6:00 AM UTC converts to 3:00 PM IRKST, which is useful when translating aviation, server, or database timestamps into local Siberian time.
When does IRKST change?
Under the historical DST system, IRKST changed to IRKT on the last Sunday in October and changed from IRKT to IRKST on the last Sunday in March. For 2026, those dates are 29 March 2026 and 25 October 2026, although modern Russian civil time no longer uses these seasonal switches in the same way after the country’s time reform.
Is IRKST the same as JST or KST because they are all UTC+9?
They share the same UTC+9 offset, but they are not the same time zone label. JST refers to Japan Standard Time and KST refers to Korea Standard Time, while IRKST specifically refers to Irkutsk Summer Time, a historical daylight saving designation tied to Russia’s Irkutsk region.
How far ahead is IRKST compared with Moscow?
IRKST at UTC+9 is 6 hours ahead of UTC+3 and therefore 6 hours ahead of Moscow during summer if Moscow is on UTC+3, though in modern Russian practice Moscow generally stays on MSK, UTC+3 year-round. That means when it is 9:00 AM in Moscow, it is 3:00 PM in IRKST, which is important for same-day scheduling between western Russia headquarters and eastern Siberian operations.
Why do I still see IRKST in old records or software?
You may still see IRKST in historical datasets, legacy operating systems, archived calendar files, transport schedules, or older enterprise software that preserved pre-2014 Russian DST rules. In those cases, the abbreviation helps identify that the timestamp was recorded during the summer-time period at UTC+9, rather than standard Irkutsk time at UTC+8.