Time Zone Abbreviations Explained: EST, PST, CET, and More

EST. PST. CET. GMT. IST. AEDT.

It's alphabet soup. And if you mix them up, your international meeting happens an hour off from when you thought.

I've made this mistake. It sucks. Here's how to avoid it.

Standard vs Daylight — The Thing Nobody Explains

Most timezone abbreviations come in pairs. One for winter, one for summer.

Standard Time (ST): The "normal" time used in winter months in countries with Daylight Saving Time.

Daylight Time (DT) or Summer Time: One hour ahead of standard, used in warmer months.

Example:

• EST (Eastern Standard Time) = UTC-5 (winter)
• EDT (Eastern Daylight Time) = UTC-4 (summer)

Get this wrong, and your meeting is off by an hour. Common mistake, very annoying.

US Timezones

The US has four main zones, each with winter and summer versions:

Eastern (ET)

EST = UTC-5 (November-March) — New York, Boston, Miami, DC, Atlanta

EDT = UTC-4 (March-November) — Same cities

Use "ET" when you're not sure which one applies. Safer.

Central (CT)

CST = UTC-6 (winter) — Chicago, Dallas, Houston, Minneapolis

CDT = UTC-5 (summer) — Same cities

Mountain (MT)

MST = UTC-7 — Denver, Phoenix, Salt Lake City, Albuquerque

MDT = UTC-6 (summer, except Arizona)

Arizona doesn't do DST. They stay on MST year-round. This trips people up constantly.

Pacific (PT)

PST = UTC-8 (winter) — LA, San Francisco, Seattle, San Diego, Vegas

PDT = UTC-7 (summer) — Same cities

Alaska and Hawaii

AKST/AKDT = UTC-9/-8

HST = UTC-10 (Hawaii doesn't do DST, no HDT)

European Timezones

Europe has three main zones:

Western European (WET/GMT)

WET = UTC+0 (winter) — UK, Ireland, Portugal, Iceland

WEST = UTC+1 (summer, except Iceland which skips DST)

In the UK, they usually say:

• GMT (Greenwich Mean Time) for winter
• BST (British Summer Time) for summer

Central European (CET)

CET = UTC+1 (winter) — France, Germany, Spain, Italy, Netherlands, Belgium, Switzerland, Austria, Poland, most of Western/Central Europe

CEST = UTC+2 (summer) — Same countries

Eastern European (EET)

EET = UTC+2 (winter) — Finland, Greece, Romania, Bulgaria, Baltic states, Ukraine

EEST = UTC+3 (summer) — Same countries

Asian Timezones

Most of Asia doesn't do DST. Simpler, but bigger time gaps to deal with.

India

IST = UTC+5:30 (year-round, no DST)

Whole country uses one timezone. That .5 hour offset trips people up.

Warning: IST also means Israel Standard Time (UTC+2) and Irish Standard Time (UTC+1). Context matters!

China

CST = UTC+8 (year-round)

Entire country on one timezone.

Big Warning: CST also means Central Standard Time (US, UTC-6). This causes massive confusion. Always clarify which CST you mean!

Japan, Korea, Southeast Asia

JST (Japan) = UTC+9

KST (Korea) = UTC+9

SGT (Singapore) = UTC+8

HKT (Hong Kong) = UTC+8

PHT (Philippines) = UTC+8

All year-round, no DST.

Australian Timezones

Australia is complicated. Three zones, only some states do DST, and their seasons are backwards from the Northern Hemisphere.

Eastern Australia

AEST = UTC+10 (April-October)

AEDT = UTC+11 (October-April)

NSW, Victoria, Tasmania, ACT do DST.

Queensland doesn't. Stays on AEST year-round.

Central Australia

ACST = UTC+9:30

ACDT = UTC+10:30

South Australia does DST.

Northern Territory doesn't.

Western Australia

AWST = UTC+8 (year-round, no DST)

Other Zones Worth Knowing

Middle East:

• GST (Gulf) = UTC+4 (UAE, Oman)
• AST (Arabia) = UTC+3 (Saudi, Kuwait, Qatar)
• IST/IDT (Israel) = UTC+2/+3

Americas:

• AST/ADT (Atlantic) = UTC-4/-3 (eastern Canada, Caribbean)
• BRT (Brazil) = UTC-3 (no DST since 2019)
• ART (Argentina) = UTC-3 (no DST)

New Zealand:

• NZST = UTC+12 (April-Sept)
• NZDT = UTC+13 (Sept-April)

The Ambiguity Problem

Some abbreviations mean multiple things. This causes chaos.

CST could be:

• Central Standard Time (US) — UTC-6
• China Standard Time — UTC+8
• Cuba Standard Time — UTC-5

14-hour difference between two of those!

IST could be:

• India Standard Time — UTC+5:30
• Israel Standard Time — UTC+2
• Irish Standard Time — UTC+1

EST could be:

• Eastern Standard Time (US) — UTC-5
• Australian Eastern Standard Time — UTC+10

Better Solution: IANA Names

Use full timezone names instead of abbreviations:

• "America/Chicago" instead of "CST"
• "Asia/Shanghai" instead of "CST"
• "America/New_York" instead of "EST"
• "Australia/Sydney" instead of "AEST"
• "Asia/Kolkata" instead of "IST"

Tools like Whenest use IANA names internally. Avoids all ambiguity.

Quick Reference

US: ET (EST/EDT), CT (CST/CDT), MT (MST/MDT), PT (PST/PDT)

Europe: WET/GMT (winter) / WEST/BST (summer), CET/CEST, EET/EEST

Asia (no DST): JST (UTC+9), KST (UTC+9), China CST (UTC+8), SGT (UTC+8), India IST (UTC+5:30)

Australia: AEST/AEDT (Eastern), ACST/ACDT (Central), AWST (Western, no DST)

Common Mistakes

Using EST in June: It's EDT in summer, not EST. Use "ET" if you're unsure.

Saying "CST" to someone in China: They think UTC+8. You meant UTC-6. Always specify "US Central" or "China Standard."

Forgetting DST transitions: "9 AM PST" means different absolute times in February vs August (when it's actually PDT).

No timezone at all: "Let's meet at 3 PM" — 3 PM where? Always specify.

Tools That Help

Whenest Meeting Planner:** Handles conversions and DST automatically. Shows times in everyone's local format.

Time Zone Converter:** Quick conversions between any zones.

Overlap Finder:** See when working hours align across zones.

Communication Tips

Include UTC offset for clarity: "3 PM ET (UTC-5)" removes ambiguity.

Use generic forms when unsure: "ET" instead of "EST/EDT," "PT" instead of "PST/PDT."

Spell out city names in important docs: "3:00 PM Eastern Time (New York)" is clearer than "3:00 PM EST."

Use tools with auto-conversion: Let Whenest show the right time for everyone automatically.

Bottom Line

Timezone abbreviations are confusing. Standard vs daylight, overlapping codes (CST, IST, EST all have multiple meanings), and DST transitions create constant headaches.

The solution: Use full IANA names when you can ("America/Chicago" not "CST"), include UTC offsets, and let tools handle the complexity.

Ready to schedule without the confusion? Try the meeting planner for automatic timezone handling. Read more about GMT vs UTC and 2026 DST dates.