Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It is often used interchangeably with UTC but is strictly a time zone.

Zulu Time is a military and aviation term for UTC (Coordinated Universal Time). The 'Z' stands for Zero offset.

Central European Time (CET) is UTC+1, used by most of Europe in winter. In summer, they switch to CEST (UTC+2).

UTC+0 is the base time standard. Countries like Iceland, Ghana, and the UK (in winter) use this zone.

Unix Time is the number of seconds that have elapsed since January 1, 1970 (UTC). It is zone-independent.

Japan Standard Time (JST) is UTC+9. Japan does not observe Daylight Saving Time.

Australian Eastern Standard Time (AEST) is UTC+10, used in Queensland, NSW, Victoria, Tasmania, and ACT.

UTC-5 is Eastern Standard Time (EST) in the US, and also used in parts of South America like Colombia and Peru.

What is the time difference between NY and London?

Typically 5 hours. When it is 12 PM in NY, it is 5 PM in London. This can change briefly during DST transitions.

Singapore Time (SGT) is UTC+8, the same as Beijing and Perth.

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Understanding Time Zones

What is UTC?

Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks. It is effectively the modern successor to Greenwich Mean Time (GMT). Time zones are expressed as offsets from UTC (e.g., UTC+1, UTC-5).

Daylight Saving Time (DST)

DST is the practice of advancing clocks during warmer months so that darkness falls later. Not all countries observe it, which causes time differences between cities (like London and New York) to change twice a year.

Meeting Planner Tips

Golden Hours: For US-Europe meetings, the best window is typically 8 AM - 11 AM EST / 1 PM - 4 PM GMT.
Asia Overlaps: Connecting US East Coast with Asia (e.g., Japan) is difficult, often requiring early morning or late night calls for one party.
Use ISO Format: When emailing times, use specific zones (e.g., "3 PM ET") or calendar invites to avoid confusion.

Time Zone FAQ

What is UTC?

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks and time.

What is the difference between EST and EDT?

EST is Standard Time (winter); EDT is Daylight Time (summer). The difference is 1 hour.

Does China have time zones?

China spans 5 zones geographically but uses only one standard time (Beijing Time, UTC+8).

When does Daylight Saving Time start?

Typically the second Sunday in March for the US and last Sunday in March for the EU.

How to convert PST to EST?

PST is 3 hours behind EST. 9 AM PST = 12 PM EST.

What is GMT?

Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London.

Is London on GMT all year?

No. In summer, the UK uses British Summer Time (BST), which is GMT+1.

What time zone is India in?

India Standard Time (IST) is UTC+5:30. No Daylight Saving.

How many time zones are there?

More than 24, due to fractional offsets (30/45 mins) like in India and Nepal.

What is Zulu Time?

Zulu Time is a military term for UTC. The 'Z' indicates zero offset.

Does Arizona use Daylight Saving?

Most of Arizona stays on MST all year. The Navajo Nation does observe DST.

What is the International Date Line?

Crossing west adds a day; crossing east subtracts a day. Located in the Pacific.

What is CET?

Central European Time (UTC+1), used by most of Europe in winter.

How to plan a meeting across zones?

Find overlapping business hours (8 AM - 6 PM) using the N28 slider.

What is UTC+0?

The base time standard. Used by Iceland, Ghana, and UK (winter).

Are time zones based on longitude?

Ideally 15 degrees per hour, but political borders distort them.

What is the earliest time zone?

UTC+14 (Line Islands, Kiribati). First to see the New Year.

What is the latest time zone?

UTC-12 (Baker Island). Last to see the New Year.

Does Russia have many time zones?

Yes, 11 zones, from Kaliningrad to Kamchatka.

What is Unix Time?

Seconds elapsed since Jan 1, 1970 UTC. Zone-independent.

How to convert CST to UTC?

CST is UTC-6. Add 6 hours to get UTC.

What is JST?

Japan Standard Time (UTC+9). No DST.

Why do we have Daylight Saving?

To make better use of daylight during working hours (historically).

What is AEST?

Australian Eastern Standard Time (UTC+10).

Is UTC the same as GMT?

Practically yes, but UTC is atomic standard, GMT is solar.

What time is it in space?

ISS uses UTC.

Does Antarctica have time zones?

Stations keep time of their supply country (e.g. NZ time).

What is a time zone offset?

Difference from UTC (e.g. UTC-5).

Can I save my cities?

N28 doesn't use cookies for city storage yet.

How to check server time?

Command: date -u

What is Pacific Time?

US/Canada West Coast (UTC-8/UTC-7).

Do all countries use DST?

No, most equator countries do not.

What is ISO 8601 format?

YYYY-MM-DDTHH:MM:SSZ

What is Internet Time?

Swatch .beats (1000 per day).

How to handle time zones in code?

Store in UTC, display in Local.

What is UTC-5?

EST (US) and parts of South America.

Time diff NY to London?

Usually 5 hours.

What is SGT?

Singapore Time (UTC+8).

Is there a global time?

UTC is the standard.

How to convert military time?

Subtract 12 from hours > 12.