World Time Starts Here

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Did Columbus find longitude?

Christopher Columbus

Columbus twice claimed to have found his longitude by timing lunar eclipses. These claims are probably inaccurate.

Panchang - Indian Astrology

Master your time - master your life

Panchang is a system based on Indian astrology, a spiritual and scientific calendar, with very practical aims.

Time Management Part II

Plans exist to be reviewed. The joy of discarding them

Adding new decisions, taking outdated ones off the list

Solstice and Stonehenge

The magic of midsummer in a magical place

Anna Monks

Time Management

It cannot be stored or saved for later. Time can only be managed

We all know the theory of how to use time better, how do we put it in practice?

What is the definition of a second?

As the definition of time evolved, so did the second's

Earth Time and Atomic Time have to be 'reconciled'


Precise Clock

NIST scientists have built a second "quantum logic clock," using quantum information processing techniques on a single ion of aluminium to make a clock that would not gain or lose more than one second in about 3.7 billion years.  

The International Meridian Conference, Washington, 1884

The Prime Meridian at Greenwich becomes the point of reference

Why is Greenwich the "centre of time and space"?

In tune, on time and in time

What is the International Atomic Time Scale?

Other links

Global Time

What time is it now across the World?

By using your computer's clock, this calculates the time in other time zones all over the world! Useful if you communicate across different time zones for business or leisure.

UTC - Universal Time Coordinated

What is Coordinated Universal Time?

Coordinated Universal Time ( UTC ) replaced Greenwich Mean Time (GMT) as the World standard for time.  UTC is based on atomic measurements rather than the earth's rotation. Greenwich Mean Time (GMT) is still the standard time zone for the Prime Meridian (Zero Longitude).

What is the SI unit of time?

Official definition of a second

Oxford Time

What is Oxford Time?

Before the coming of the railways (railroad) every town had its local time.  With the introduction of Railway Time , time zones and Standard Time became the norm.



First the event: intuitively, we can think of two events as being simultaneous - at the same time - or consecutive - one after the other.

Lunar Calendars

Measuring Time by Days and Months

We do not know how the concept of measuring time was first grasped, but we can see that early calendars are based on natural cycles. These could be:

British Summer Time

British Summer Time (BST) is the UK name for Daylight Saving Time

In 2017 BST runs from Sunday 26 March 01:00 GMT - Sunday 29 October 01:00 GMT (02:00 BST)

Calendar Systems

The systems that sort out the year

The last millennium would have been celebrated in Greenwich, England on 25 March 1001 AD but it wasn't a thousand years ago because we "lost" 11 days along the way!


Network Time Protocol

NTP is a protocol designed to synchronize the clocks of computers over a network. NTP version 3 is an internet draft standard, formalized in RFC 1305. NTP version 4 is a significant revision of the NTP standard, and is the current development version, but has not been formalized in an RFC. Simple NTP (SNTP) version 4 is described in RFC 2030.

Astrology: Natal Chart

The planets at the moment of your birth

Astrologers believe that the planets at the moment  of your birth have key influences on your personality.  In order to calculate your Natal (or birth) Chart you will need to know the Time and Place of your birth.  Most people know their Sun sign (the position in the zodiac that the Sun was in on your birth-date.  The position of all the planets is described in your Natal Chart.  You will also need an Ephemeris to help calculate this.

GMT - Greenwich Mean Time

Global Time Zones - What time is it anywhere in the World?


Zulu Time

What is "Zulu" time?

"Zulu" time , more commonly know as "GMT" ( Greenwich Mean Time ) is time at the Zero Meridian.  Our natural concept of time is linked to the rotation of the earth and we define the length of the day as the 24 hours it takes (on average) the earth to spin once on its axis.

From Plot Device to Philosophy : Shakespeare and Time

Measuring Time in the 16th Century

Perceptions of time were changing in 16th Century Europe. Education was based on rediscovered Greek and Latin writers and their Histories. At grammar school in Stratford, Shakespeare gained knowledge of centuries of European history. Meanwhile, technologists were trying to develop accurate clocks to help the merchant ships sailing to the Americas and Indies. Navigators struggled to find correct longitude without accurate timepieces. In the Merchant of Venice, Salerio refers to the “sandy hour-glass” when describing Antonio’s ships in danger at sea.

Bristol Time

What is Bristol Time?

Before the railways (railroads) came, there was no particular reason why people in  Bristol, England should keep the same time as people in London.  At that time there was no practical way of communicating information about time over a distance. When the telegraph made such communication possible, it became necessary for people living in one area to agree that they would not keep their own local time, but would all keep a time based on the local standard meridian. Bristol is at 2º 35' W(est) of Greenwich, so when it is noon in Bristol is just past 10 past noon (twelve) in London.

Summer Time

Daylight Saving Time

There are 25 integer World Time Zones from -12 through 0 (GMT) to +12. Each one is 15° of Longitude as measured East and West from the Prime Meridian of the World at Greenwich, England.

GMT Timestamp

GMT Server Time Stamp:

The upper time stamp is taken from our server which is synchronized to the NTP network and should be accurate within 1 second. The lower timestamp is the time on your computer , converted to GMT. Therefore, if your computer's time is correct, there should not be more than a 2 second difference between the upper and lower time stamps. The extra second is to allow for network delay and the conversion process from your computer's time to GMT.

Why is the Navy so involved in time-keeping?

The earliest users of accurate time were the navy

Precision is not optional at sea

BBC Pips

Greenwich Time Signal

For 75 years the major global news headlines of the day have been preceded by the six Greenwich Time 'pips'.  When the news of Neil Armstrong's first steps on the moon , President John F Kennedy's assassination and the destruction of the Berlin Wall were broadcast across the world on the BBC, they followed the familiar sound of the Greenwich pips.

Time Ball

What time does the time-ball drop at Greenwich?

In 1833 a red "Time Ball" was installed on the roof of the Royal Observatory Greenwich

World Time Zone Map

Map of Global Time Zones

A Brief History of British Summer Time (Daylight Saving Time)

Standard Time Becomes Normal

At the equator the day lasts 12 hours with slight annual variation. As latitudes increase so does the variation between winter and summer day-length. For thousands of years this was not a problem as people could organise their days locally around the sun, moon and season. However, industrialisation and urbanisation led to common working hours and by the 19th century many people lived by the clock. Standard times were adopted in response to the spread of railways and telegraphic communications. In 1880 in Britain the clocks were set to Greenwich Mean Time (GMT) i.e. when the sun is at its highest in the sky it is 12 noon at Greenwich.

Railway Time

Standard Time

The History of Time Zones

Standard time the time of a town, region or country that is established by law or general usage as civil time.  It is determined locally.  The whole of China, one of the largest countries in the world, has decided to adopt a single time zone

Military & Civilian Time Designations

From Time Zone A - Z

There are 25 integer World Time Zones from -12 through 0 (GMT) to +12. Each one is 15° of Longitude as measured East and West from the Prime Meridian of the World at Greenwich, England. Some countries have adopted non-standard time zones, usually 30 minutes offset which have a * designation.

Roman Numerals

Why do clocks use IIII instead of IV for 4?

A.M. and P.M.

What is Noon and Midnight?

A.M. and P.M. start immediately after Midnight and Noon (Midday) respectively.


History of Sundials

All in One: World and Local Clocks

Digital timepieces for real and virtual travel

Any world clock provides by definition the time in various parts of planet Earth, including all timezones. As the world is made up of a multitude of local times, a better name for such a timepiece would be “The World is Local”.

British Summer Time (BST) Dates Since 1950

When did summer time start and end ?


How GMT is being used today?

Uses of GMT go from email time stamp to air travel


Prime Meridian

Longitude Zero

Agreeing on a universal Prime Meridian was not an easy affair.

Time and Cricket

A complex relationship

Anna Monks

Greenwich Mean Time (GMT) - World Time

How to view local current time differences

GMT is both a timezone and the reference point for the Prime Meridian. The United Kingdom runs on GMT only during Winter months and on BST during Summer months: British Summer Time (BST). British Summer Time is in its way unique, not just because of its name. As it so often happens, scientific facts provide unusual insights. {{ snippet.clock_panel(title_1="London Time", timezone_1="Europe/London", page_link_1=None, title_2="GMT", timezone_2="GMT", page_link_2=None) }}

Frequently Asked Questions - FAQs

The International Meridian Conference

Washington DC, USA - October 1884

From pages 199 to 204:

Mardi Gras

"Fat" or Shrove Tuesday

First, determine the date for Easter of any given year (which is the first Sunday after the first full moon that follows the Spring Equinox) and then count back 47 days (40 days of Lent plus Holy Week) to find Mardi Gras Day.

The International Meridian Conference

Washington DC, USA - October 1884

Extract from one of the middle sessions of the Conference:

ISO Time

What is the time in ISO format?

The International Organization for Standardization ( ISO ) is a worldwide federation of national standards bodies from some 130 countries, one from each country.

Time is money?

Leap Second

The adjustment between Atomic & Earth Time

The Coordinated Universal Time (or UTC) replaced Greenwich Mean Time (GMT) as the reference time scale derived from The Temps Atomique International (TAI) calculated by the Bureau International des Poids et Mesures (BIPM) in Paris, France using a worldwide network of atomic clocks. UTC differs from TAI by an integer number of seconds; it is the basis of all activities in the world.

A Chinese New Year

New Zealand at Autumn Equinox Time

The Winter Solstice

Time Websites

Royal Observatory Greenwich

The Royal Observatory Greenwich has a wide-ranging treasure trove of information on time & Astronomy.

Free Newsletter

It's official: we're ruled by time

Time is the most popular common noun in English

We like to be punctual, we expect our trains to run to schedule, and many of us spend our working day watching the clock. Now the new revised eleventh edition of the Concise Oxford English Dictionary can officially confirm that we are indeed ruled by time .

Name of Months

Month names ~ every major European language

A linguist's calendar

Days of the Week

Official European Union Languages

A multi-lingual Monday to Sunday

UK Clock Changes and the Anatomy of a Second

GMT, BST, UTC - plus EU legislation

Summer Period - The Full Story

When did the millennium begin?

This millennium (and century) officially began on: 1 January 2001 GMT

The simple explanation is that our Calendar System began at 1AD.  There was no year 0.  The calendar we use today goes from 1BC to 1AD.

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