Time in Chiang Mai: Time Zone, UK Time Difference and When It Changes

A HelloRoam Thailand eSIM gets your phone online on AIS, DTAC or TrueMove H, depending on the plan, as soon as you land, and 24/7 support is on hand if it does not connect. From there, the phone's automatic time zone setting can switch the clock to Thai time before your first tour pick-up, hotel check-in or call home.

Chiang Mai is 6 hours ahead of the UK in summer and 7 in winter

Chiang Mai's clock never changes, but the UK's does, so the gap depends on when you travel. GOV.UK lists the next few UK clock change dates and the rule behind them: forward 1 hour at 01:00 on the last Sunday in March, and back 1 hour at 02:00 on the last Sunday in October. British Summer Time (BST) is the period when UK clocks are 1 hour ahead of Greenwich Mean Time (GMT).

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Clock websites only show the gap on the day you look. If you check in early October for a December trip, the 6 hours on screen will be 7 by the time you fly.

UK times converted to Chiang Mai time

Add 7 hours to UK time in winter and 6 hours in summer. From 17:00 in the UK in winter, or 18:00 in summer, it is already the next day in Chiang Mai.

Going the other way, take off 7 hours in winter and 6 in summer. A Chiang Mai breakfast falls in the middle of the British night.

Chiang Mai afternoons and evenings overlap with the UK working day

A UK office day of 09:00 to 17:30 runs from 16:00 to 00:30 in Chiang Mai while the UK is on GMT, and from 15:00 to 23:30 while it is on BST. Working UK hours from Chiang Mai means a mid-afternoon start and a finish near midnight, with the local morning free. Our page on data plans for remote workers abroad covers staying online for that kind of trip.

For calls to family, Chiang Mai evenings are the easy slot, because they fall between late morning and mid-afternoon in the UK. Video calls over WhatsApp or FaceTime run on mobile data away from Wi-Fi, so estimate your trip's data needs before you pick a plan.

All of Thailand shares one clock with Laos, Cambodia and Vietnam

Chiang Mai has no time zone of its own. The whole of Thailand keeps one clock, which the National Institute of Metrology (Thailand) calls Thailand Standard Time. The institute keeps the national reference, UTC(NIMT), on caesium clocks compared with world time by the International Bureau of Weights and Measures (BIPM), as its standard time service page explains. Clock websites usually label the zone Indochina Time (ICT).

In the IANA time zone database, Chiang Mai falls under Asia/Bangkok. That zone has run at UTC+7 since April 1920, when Thailand dropped Bangkok Mean Time, and it has no daylight saving rule. It also covers Laos, Cambodia and northern Vietnam, so if a calendar app asks for a time zone, choose Bangkok.

If Chiang Mai is one stop on a longer trip, our Thailand holiday guide for UK travellers covers the rest of the country. If you are carrying on to Laos or Vietnam, both on Chiang Mai's clock, a regional plan for Asia from HelloRoam keeps one eSIM working across those borders.

Thai dates count the year from the Buddhist Era

Thai dates often give the year in the Buddhist Era, which runs 543 years ahead of the Western calendar. That makes 2026 the year 2569, and 2027 will be 2570. The National Institute of Metrology, for example, dated its seminar news post from September 2026 as 23 September 2569.

If a date on Thai paperwork shows a year in the 2500s, take off 543 to find the year you know.

Chiang Mai mornings are coolest from December to February

Chiang Mai does get cool, but mainly at dawn. Long-term averages from the Thai Meteorological Department, published on the World Meteorological Organization's Chiang Mai page, put January's average low at 14.2°C, with afternoons near 29°C. By April the average high reaches 36.1°C, and August has the most rain, at 224.6 mm over about 21 days.

From December to February, a light layer covers early starts and late evenings. The same months are the driest, with under 2 rain days a month on average.

Two settings on iPhone and two on Android put the clock on Thai time

Phones set the local time zone themselves when their automatic settings are on. On an iPhone, Apple's time and time zone guide lists two settings: Settings > General > Date & Time > Set Automatically, and Settings > Privacy & Security > Location Services > System Services > Setting Time Zone. If the clock still shows UK time, Apple's fallback is to turn off Set Automatically, tap Time Zone and enter a city in the zone you need, such as Bangkok.

Android menus vary by maker. Google's Clock app help page gives Clock > More > Settings > Change date and time, where you turn on Automatic date and time and Automatic time zone. With Use location on, the phone may also use its location to find the zone. For timing calls home, Automatic home clock in the Clock settings adds a UK clock while you are in Chiang Mai.

Apple's first step is making sure the phone is online, so the switch happens once you have a connection in Thailand. If you are travelling with a HelloRoam eSIM, install the eSIM before you fly, while you still have home Wi-Fi, so it is ready to connect when you land.