Understanding Time Zones on Chess.com: Never Miss a Tournament Again

Back to TopWelcome back my friends,
This is @DocSimooo, as always at your service.

This time we'll talk about checkmating the clock, understanding Global Time Zones on Chess.com! Are you ready?

Chess.com is a global platform with users all over the world.
Daily tournaments, team matches and Rapid, Blitz, and Bullet Live Arenas are held every day.
If you’ve ever joined a Chess.com tournament only to realize it started hours ago (or will start in the middle of the night), you’re in good company.
Same thing happened to me—I misunderstood the exact start time more than once.

Time zones can be tricky—especially when events are announced in different formats or when daylight saving time kicks in.
Here’s a simple guide to help you make sense of it all so you’ll never miss your next Arena or Daily event again.
I hope this is helpful. Enjoy the reading.

Understanding Time Zones on Chess.com: Never Miss a Tournament Again

TABLE OF CONTENTS 

Preface

Introduction
The Reasons for Time Zones and Seasons
- Premises
- What Are Time Zones and Why Do They Exist?
- Daylight Saving Time (DST) or Summer Time
- The Reasons for the Seasons
The Time Zone Notations
How to Read Time Zone Abbreviations
Amusing Time Zone Anecdotes
Global Time Zones on Chess.com
- Time Zone Abbreviations in Use? Checkmate the Clock !!
- Announce Your Tournament Times Correctly
Epilogue

Appendix

Introduction

This post aims to help understand the different time zone notations, so we can avoid making mistakes in scheduling—like signing up for tournaments in the middle of the night or at times completely incompatible with our daily routines, just because we misunderstood the correct start time.
Let’s begin.

The Reasons for Time Zones and Seasons

Premises

Our wonderful planet Earth, which is part of the solar system, while making its revolution around the Sun in a long journey that takes 365 days to complete, also rotates on its own axis in 24 hours. The passing of days, with the alternation of day and night, is due to this rotation.

The Earth has the shape of a geoid, which can be roughly approximated to a sphere flattened at the poles, with truly considerable dimensions: the equatorial diameter is 12,756 km, and the polar diameter is 12,714 km. The circumference of our planet is about 40,000 km.

The Earth's surface is covered by about 71% water and the remaining 29% by land (continents and islands).
There are six continents: Europe, Asia, Africa, the Americas, Oceania, and Antarctica, and at least 193 sovereign nations.

Meridians and parallels are imaginary lines that form a grid—an imaginary reference system on the Earth’s surface that makes it possible to determine the exact position and distance of any point relative to an observer through the coordinates of latitude (parallels) and longitude (meridians).

Thanks to latitude and longitude coordinates, it is possible to locate any place precisely and unambiguously.

 

Ok, but...
What Are Time Zones and Why Do They Exist?

As already mentioned, our planet Earth, while orbiting around the Sun, rotates 360° on its own axis every 24 hours—meaning about 15° per hour. This is the fundamental reason for the constant alternation of day and night.

Daylight Saving Time (DST) or Summer Time

Daylight saving time complicates things a little. It’s a system adopted to make better use of the hours of sunlight.

Moving the clocks forward in spring allows people to enjoy longer and brighter days throughout the summer. This means making greater use of natural light and delaying the need to turn on artificial lighting.
Daylight saving time is observed in most of Europe, in North America, and in some areas of the Middle East from late March to late October or early November.
In countries of the Southern Hemisphere (such as Australia, New Zealand, and Chile), daylight saving time is observed, but during periods opposite to those in the Northern Hemisphere — generally from late September to early April — since the seasons are reversed in those regions.

There are many countries, however, where daylight saving time is not observed at all: in equatorial and tropical countries, where the length of day and night does not change throughout the year; in many Latin American countries; and in almost all of Asia and the African continent.

In Italy, daylight saving time (+1) is in effect from March 30 to October 26.
It allows for significant energy savings by making better use of natural sunlight during the evening hours. Lower electricity consumption results in a reduction of carbon dioxide (CO₂) emissions. Energy savings also lead to lower electricity bills for households and for the energy system as a whole. In autumn, the clock is then set back by one hour.

The debate over the actual usefulness of daylight saving time remains open, due to its negative effects on health and sleep caused by the “micro jet lag” that results from moving the clock forward and backward.

The Reasons for the Seasons

The Earth's axis is tilted by about 23.5° relative to the plane of its orbit around the Sun (the ecliptic).

Because of this tilt, the Sun’s rays hit different parts of the planet at different angles during the year, so each hemisphere alternates between receiving more or less sunlight.
The seasons of the year do not depend on the distance between the Earth and the Sun, but rather on the tilt of the Earth's axis relative to the Sun’s rays.
Summer occurs when a hemisphere is tilted toward the Sun (its pole is directed toward the Sun). The other hemisphere, in turn, experiences winter.
Winter occurs when a hemisphere is tilted away from the Sun. The other hemisphere then experiences summer.
After six months, the situation reverses.

In spring and autumn, the Earth's axis of rotation is perpendicular to the direction of the Sun’s rays: day and night have the same length, and the season is mild in both hemispheres.

This happens when the ecliptic — the plane along which the Earth revolves around the Sun — intersect or is close to the celestial equator.
The celestial equator is the projection of the Earth's equator onto the celestial sphere, and it is a circle that divides the Earth into two celestial hemispheres: the northern and the southern. It is perpendicular to the Earth's axis of rotation.

Solstice and equinox

A solstice is the time or date — twice each year — when the Sun reaches its maximum (+23.4°) or minimum (−23.4°) declination, passing through 0° at the equinoxes.
Declination is the angle between the Sun’s rays and the plane of Earth’s equator. It varies throughout Earth’s annual revolution around the Sun.

The maximum declination is about +23.4° and the minimum about −23.4°, which correspond to the tilt of Earth’s rotational axis relative to the plane of its orbit — an angle that remains always constant at about 23.4°.
This axial tilt is what causes the change in the Sun’s apparent position in the sky throughout the year and the seasons.

At +23.4°, the Sun is farther north and higher in the sky → northern summer, longer days.
At −23.4°, the Sun is farther south and lower in the sky → northern winter, shorter days.
So, a solstice marks the longest and shortest days of the year (around June 21 and December 22).

An equinox is the moment when the Sun’s rays are perpendicular to Earth’s equator — the Sun crosses the celestial equator, moving either northward or southward in the sky.
The word equinox comes from Latin: aequus (“equal”) + nox (“night”), literally meaning “equal night.”

At an equinox, the Sun’s declination = 0°, meaning it is directly above Earth’s equator. The Sun’s rays strike the equator perpendicularly, and day and night are each about 12 hours long everywhere on Earth. 

In summary:

• June 21 (summer solstice in the Northern Hemisphere):
  The Northern Hemisphere is tilted toward the Sun → receives more light and heat → summer in the north, winter in the south.
• December 21 (winter solstice in the Northern Hemisphere):
  The Southern Hemisphere is tilted toward the Sun → receives more light and heat → winter in the north, summer in the south.
• March 21 and September 23 (spring and autumn equinoxes):
  Earth’s axis is not tilted toward or away from the Sun (the Earth’s axis is always tilted 23.5° relative to the plane of the ecliptic, but its orientation relative to the Sun is such that neither hemisphere is tilted toward or away from it) → day and night have equal length → spring/autumn in both hemispheres, but reversed.

Time Zone Notations

Ok, we’ve already seen and understood why, at the same moment, different places in the world have different times and seasons.
So, what are the time zone calculation systems that have been adopted?
The first global time zone system was GMT — an acronym for Greenwich Mean Time.
It’s the reference time zone used since 1884, based on the prime meridian located in Greenwich, London.
In the military phonetic alphabet, it’s known as “Zulu Time” (where Zulu stands for the letter Z, meaning zero).
Today, the GMT system has been largely replaced by Coordinated Universal Time (UTC), but UTC is almost identical to GMT and still uses the Greenwich meridian as its zero reference.

This system of measuring time is clear and unambiguous.
It does not change with daylight saving time and helps avoid confusion between different time zones.

UTC with Offset

12:00 UTC±hh(:mm) → indicates the time clearly and without ambiguity.
“+” = ahead of UTC (meridians east of Greenwich)
“–” = behind UTC (meridians west of Greenwich)

Examples:

12:00 UTC → noon at the zero meridian, London
12:00 UTC+1 → 13:00 in Rome, Italy
12:00 UTC–1 → 11:00 in Reykjavík, Iceland

There are other (less common) systems used to express time unambiguously:

IANA time zone names (e.g., “Europe/Rome” or “America/New_York”):

2025-10-20T15:30[Europe/Rome]

ISO 8601 → date/time with a suffix:

e.g., 2025-09-30T12:00Z = UTC (the “Z” stands for Zulu = UTC)
e.g., 2025-09-30T12:00+02:00 = UTC+2

There are also abbreviations for each geographic area. They are convenient but often ambiguous, since they can vary depending on whether daylight saving time is in effect or not. 

How to Read Time Zone Abbreviations

Here are the most common abbreviations for each region — just remember to check the season, as daylight saving time may apply.

Europe
WET / WEST = Western Europe (UTC+0 / +1)
CET / CEST = Central Europe (UTC+1 / +2)
EET / EEST = Eastern Europe (UTC+2 / +3)
BST = British Summer Time (UTC+1, UK summer)
IST = Irish Summer Time (UTC+1).

Americas
AST/ADT = Atlantic (UTC−4 / −3)
EST / EDT = Eastern (UTC−5 / −4)
CST / CDT = Central (UTC−6 / −5)
MST / MDT = Mountain (UTC−7 / −6)
PST / PDT = Pacific (UTC−8 / −7)
AKST/AKDT = Alaska (UTC−9 / UTC−8)
HST = Hawaii (UTC−10, no daylight saving)

Asia & Oceania
AST = Arabia Standard Time (UTC+3)
IST = India (UTC+5:30)
CST = China Standard Time (UTC+8)
HKT = Hong Kong (UTC+8)
JST / KST = Japan / Korea (UTC+9)
ACST / ACTD = Adelaide (UTC+9:30 / +10:30)
AEST / AEDT = Sydney, Melbourne−Australia (UTC+10 / +11)
NZST / NZDT = New Zealand (UTC+12 / +13)

If you see a short abbreviation (like PST or CEST), always check the region and whether daylight saving is active.

Amusing Time Zone Anecdotes

The International Date Line corresponds to the 180th meridian of longitude and crosses the Pacific Ocean roughly halfway between Asia and the Americas, near the Fiji Islands and New Zealand.

The Biggest Time Gaps on Earth

If you only count inhabited places, the largest practical difference is 25 hours, between Kiritimati (UTC+14) and Pago Pago, American Samoa, U.S. (UTC−11).

And here’s a wild one:
Two Diomede Islands in the Bering Strait are only about 4 km apart, but they’re 21 hours apart in time!

Big Diomede (Russia) → Asia/Anadyr = UTC+12:00

Little Diomede (USA) → America/Nome = UTC−09:00 (or −08:00 during Daylight Saving Time)

Although geographically adjacent, Little Diomede follows the Alaskan time zone because it is part of the United States.

Actual difference:

From UTC−09:00 to UTC+12:00 = 21 hours (not 24).

When Alaska observes Daylight Saving Time (UTC−08:00), the difference decreases to about 20 hours.

As I already said, time zone borders don’t run straight down the map — they often shift to follow national boundaries or to prevent people in the same city from living in different time zones. A curious case is China, which uses a single official time across its vast territory, even though it spans five geographical time zones. France, on the other hand, covers the greatest number of time zones in the world thanks to its overseas territories.

Have a look — 61 second video

Global Time Zones on Chess.com

A reassuring premise is that, in general, Chess.com automatically adjusts times based on each user’s local time zone, so there’s no ambiguity about tournament schedules.

However, the local time zone must be set by the user, and this can be easily done as follows:
On the website: Settings → All Settings → Profile → Details → Timezone

Time-zone abbreviations can cause confusion when they’re used without explanation in event announcements. This really happens—even in official posts and messages from coaches or instructors—where start times are given with an abbreviation but no context.

Before relying on them, it’s a good idea to double-check what the abbreviation actually means — some can refer to different time zones depending on the region.

So make sure to confirm the time and convert it to your local zone, keeping in mind whether daylight saving time might be in effect where the event takes place.

For example:
If a tournament starts at 12:00 noon, Pacific Time (U.S. West Coast), you might see the announcement written like this:

01/13/2026 12:00 PST → 20:00 UTC → 21:00 CET (winter)
07/18/2026 12:00 PDT → 19:00 UTC → 20:00 BST (UTC+1) → 21:00 CEST (summer)

That means the local time in Rome (CET / CEST = Central Europe) stays the same (21:00), because both the U.S. Pacific Coast and Central Europe observe daylight saving time — but the offset from UTC changes with the season.

In detail:
Winter: 12:00 PST = UTC−8
Summer: 12:00 PDT = UTC−7 = BST (British Summer Time)−8h
Winter: GMT = UTC+0
Summer: BST = UTC+1
Winter (CET): Italy = UTC+1
Summer (CEST): Italy = UTC+2

Tools to Double-Check Your Local Time
When in doubt, just use an online time converter like time.is/compare or worldtimebuddy.com — or simply ask ChatGPT, of course! 😆

Announce Your Tournament Times Correctly

The clearest way to communicate the date and time of an online event is to rely on Chess.com’s automatic system.
When you announce a tournament, just enter the event time and share the link — everyone will see the correct time in their own time zone.

Be careful when choosing the time: if most Club members live in time zones far from yours, it’s good practice to pick a time that fits their waking and working hours.
Try to avoid scheduling events in the middle of the night for them — or during typical office hours.

Whenever possible, specify the time using the UTC system.
If you prefer to use time zone abbreviations, make sure to include their full meaning so that everyone can understand them. I had to write a whole blog post just to figure that out myself! 😆

For example: event scheduled for November 15 at 19:45 UTC or 20:45 UTC+1
or November 15 at 20:45 CET (Central European Time).

You could include a link to a time conversion tool such as time.is/compare or worldtimebuddy.com.

That way, no one will ever miss a tournament because of time confusion!

Epilogue

In Short:
Chess.com is global — players connect from every continent, and time zones can get messy fast.
But with a bit of awareness you can always show up on time for your next tournament!

Take care of the members of your Club: make sure to state the time clearly so there's no confusion.

Best practice (in my view):

• Use UTC: “Starts at 18:00 UTC on 12 Nov.”
• Add offset + city: “Starts at 6:00 pm (UTC-5, New York) on 12 Nov.”
• Spell it out: “Starts at 6:00 pm Eastern Time (UTC-5) on 12 Nov.”

Avoid ambiguous abbreviations like CST, IST, AST without clarification—they map to multiple regions.

Because no one wants to lose before the first move — to the clock!

Well then, it’s your turn!
Do you ever get confused by time zones?
Have you ever missed the start of a tournament or misunderstood the right starting time?

I hope this post helped to clear things up — and that you found it both useful and enjoyable to read.

Warm regards,
DocSimooo

Appendix

Why Do We Have Different Seasons? | California Academy of Sciences

14 Amazing Facts About Time Zones