Time Service

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Time Signal and Time System in South Africa

.Noon Day Gun

. Timeball

In Brief:

Science was introduced to the Southern Hemisphere in order to provide a time signal!

The major problem facing seafarers and navies was one of accurate navigation. It was known as the problem of Longitude. To solve the problem an accurate time signal was required. A Cannon fired at a given time (now known as the Noon Day Guns) to signal a specific time so that Navigators can reset their chronometers (pocket watches) to the Standard time for Cape Town. The precise moment to fire the cannon was left to scientifically untrained people, so accuracy was lacking. This led to the establishment of an Astronomical Observatory, which became the first permanent scientific establishment in the Southern Hemisphere, in order to provide an accurate time signal to the Royal Navy. The firing of the Noon Day Gun in Cape Town is also the oldest continuous time signal in the world.



Observatories involved:
Royal Observatory, Cape of Good Hope
Johannesburg Observatory.
Various flare pistols
Two Cannons
Various Timeballs
.Duration: 1806 to today


Accurate Navigation was one of many serious challenges facing seafarers. The problems were many, from inaccurate maps to incompetent navigators. To prevent a vessel from running onto rocks you need excellent men on lookout duty, but also accurate navigation. To express where you are on Earth navigators created an imaginary grid system of lines running east-west crisscrossed by lines running north-south. The two sets of lines are different, requiring different expressions and reference systems.The east-west lines are referred to as Latitude and are used to plot how far north or south you are of the equator.  (it is confusing but take a globe of the earth and figure it out.). The lines run parallel to each other. Using this system requires a sextant to plot the angle of stars.The other system use lines drawn between the north and south pole, These lines are referred to as Longitude and they are not parallel to each other. These lines indicate how far East or West you are from your destination. The main instrument used is a watch. To infer your position you determine the local time and compare it to the actual time of your destination. The difference is expressed in degrees, hours, minutes and seconds.To clarify the basic aspects of navigation please read the excellent book called “Longitude” by Dava Sobel. In summary, to navigate accurately you require not only a sextant but also an accurate watch. You also require a method of accurately resetting the watch, and this is where a time signal comes in.The first permanent scientific establishment in the Southern Hemisphere was created in Cape Town, South Africa in order to provide an accurate time signal to navigators! This establishment became known as the Royal Observatory, Cape of Good Hope. The time signal was given by firing a flare pistol, drop time balls, and most spectacularly of all, by firing a cannon. The cannon is the oldest cannon in the world firing a continuous time signal and is known as “The Noon Day Gun”A History:
The Cape Colony was started in 1652 by the Dutch East India Company, the most powerful company in the world at the time. They developed a cannon signaling relay system but did not use it for signaling time. Britain annexed the Cape Colony and at the time was the most powerful seafaring nation in the world and accurate navigation was of crucial importance. Thus they instituted a time signal system.Britain annexed the Cape Colony in 1795 and ruled it until 1803. In this time (1798) there is a reference that a cannon firing a time signal set  a Naval Store on fire. [Green] The British returned the Cape Colony to Dutch Rule and this became known as the Batavian Period, 1803 to 1806. No known reference about a time signal is known to the author during this time.Britain took the Cape Colony for a second time and ruled it from 1806 until 1961. During this period the time signal at the Cape as we know it today was introduced. In 1806 (possibly 1807) the British authorities instituted the firing of 18 pounder guns from Imhoff Battery [Bisset / de Vries, pp42-3] Later on cannons in the Castle at Good Hope was used.The purpose of a firing the cannon is to provide an accurate time signal. Gunners are not trained scientist and how they accurately determined when to fire is unknown. In order to rectify this situation a radical solution was needed.

Due to a request made by the Royal Astronomical Society (with John Herschel as first president) the British Admiralty decided that there was a need to establish the Board of Longitude to help improve good navigation, an aspect essential to the expanding naval dominance of the British Empire. In 1820 the Board of Longitude asked for a permanent observatory to be settled in South Africa to help solve navigational needs. They envisaged an observatory in the Southern Hemisphere to complement the work at Greenwich Observatory in the north, including the provision of a “time service” for ships calling there. [Smits; Laing, p. 3] An Order of Council of His Majesty King George IV established the Observatory at the Cape of Good Hope on 20 October 1820. The stated purpose: The improvement of practical astronomy and navigation.  [Laing, p. 8. Warner – Astronomers, p.2]

It took a long time to set up the Observatory and get it into working order. It was only the second astronomer at the Royal Observatory, Thomas Henderson, who in 1833 started firing a time signal with a flare pistol. He stood on the roof of the Observatory and fired the pistol at night at “an advertised time”. The flash of the pistol was visible to the ships in Table Bay. This was the start of accurate time signals. [Warner – Astr, p.34]

In 1829 the time ball was invented by Robert Wauchope. They would hoist a big brightly painted ball up a pole and at a given time the ball would be dropped. In 1836 a time ball with a diameter of 5 ft was erected on the grounds of the Royal Observatory. [Warner – Astr, p.47. / Kinns, p.98]  In time the original time ball could not be seen due to the growth of trees. A bigger time ball was installed on the Observatory terrain by 1853. The Time ball service was also extended to Signal Hill and Simon’s Town as disks at end of an mechanical arms that were dropped. [Warner – Astr, p.64. / Kinns, pp.98-9].

In September 1861 a mind blowing event occurred. The time ball at the Observatory, as well as those in Simon’s Town (approximately 21 miles / 35 km) and Port Elizabeth (approx. 470 miles / 750 km) were dropped by a telegraph signal originating from the accurate time clock at the Royal Observatory. This was possibly the first time an object was remotely controlled in Southern Africa! [Cape Almanac, 1853 – 1875]. In 1883 (some sources say 1873 [Kinns p99]) a 17 ft diameter time ball was erected in the dockyard in Cape Town. This was renovated in 1997 and forms part of the backdrop to the modern Waterfront in Cape Town.

In the meantime the cannon was still firing dubiously accurate time signals from the Castle in Cape Town at one o’clock in the afternoon (13:00). Due to the growth of the town and the rattling of windows it was decided to move the cannons out of town to Lions Battery on Signal Hill. On 4 August 1902 the cannon fired for the first time from there and the time was changed to 12:00. This is the Noon Day Gun as we know it today. By 1914 the cannon was fired remotely by telephone signal from the Observatory. [Report of H.M. Astronomer at the Cape of Good Hope for the year 1914] To be more correct, there are actually two cannons fired alternatively. They are 18 pounder cannons designed by Sir Blomefield in 1786 and casted by Simon Walker and Co. Since the cannons moved to Lions Battery a total of 5 cannons have been used over the years. [de Vries, pp42-3] At present the cannons are fired every day except on Sundays and public holidays. To state the obvious, they fire blanks otherwise many buildings would be damaged  and people killed over the decades.

The Noon Day Gun was not the only Cannon signaling time in South Africa. In Simon’s Town – the main harbour for the Royal Navy in the Southern Hemisphere – a cannon was fired from a ship to signal the time. This cannon was taken into use about 1840 until 1934. Initially it was fired at 20:00 and later it was changed to 21:00. The signal became known as the 9 o’clock gun. During times of war such as the Anglo Boer War and World War One the firing also signaled the start of a curfew. [de Vries, p.44]


Chronology of Time in South Africa:

  • Since time immemorial the different indigenous tribes had their system of time keeping and calendars.
  • 1582 – 84: Gregorian Calendar accepted by most Catholic Countries.
  • 1652: Dutch East Indian Company settle a refreshment station at Table Mountain. The Calendar used by the Companu was the Gregorian Calendar.
  • 1752: Great Britain and her colonies adopts Gregorian Calendar (Cape Colony not yet part of Britain)
  • 1795 – 1803: 1st British Occupation. British authorities fires cannon from the Castle as time signal for navigational purposes.
  • 1806: 2nd British Occupation. British authorities fires cannon from the Castle as time signal for navigational purposes.
  • 1820: The “Royal Observatory at the Cape of Good Hope” (ROCGH) was founded in order to establish accurate time for the time signal. The reason for existence was to provide a time service, Astronomy was the means to achieve the goal.
  • 1833: Thomas Henderson started firing a pistol as a time signal from the roof of the Main Building of the ROCGH which was visible from the harbour.
  • 1836: Time Ball dropped from the grounds of the ROCGH
  • 1853: Time Ball service extended to Signal Hill and Simon’s Town.
  • 1859: First Railway as well as Telegraph line in Southern Africa.
  • 1861: Time balls were dropped at Simon’s Town (approximately 21 miles / 35 km) and Port Elizabeth (approx. 470 miles / 750 km)  by a telegraph signal originating from the accurate time clock at the Royal Observatory. This was possibly the first time an object was remotely controlled in Southern Africa!
  • c.1860’s: Railway lines and telegraphs. Standardized time was based on the meridian of the ROCGH in Cape Town and was referred to as “Observatory Time”. Major towns had two public clocks, one showing “Observatory Time” and the other showing local time.
  • 1902: The firing of the cannon as time signal was moved from the Castle at 13:00 to Lions Battery on Signal Hill at 12:00.
  • 1903: “Transvaal Meteorological Department” (TMD) established in Johannesburg and this would evolve to become an astronomical observatory known as Transvaal Observatory (1909 – 12); Union Observatory (1912 – 61) and Republic Observatory (1961 – 71)
  • 1903: South African Standard Time (SAST) was fixed to 30th Meridian (GMT+2 hours), a north south line running between Jhb and Durban.
  • 1905: David Gill (ROCGH) suggest that the TMD should take responsibility for SAST since it is located close to 13th Meridian.
  • 1908: The TMD take control of SAST and supply a time signal to the “South African Broadcasting Corporation” (SABC) (McDowell, p.10)
  • 1910: Due to a grant the Transvaal Observatory employ two2 part time observers to accurately determine time using the transit method. (McDowell, p.11)
  • 1912: Union Observatory extends time service to Durban by dropping a time ball via telephone signal.
  • 1923: Union Observatory discover that it is cheaper and more accurate to listen in to a time signal broadcasted from Rugby in England. Stop meridian method (McDowell, p.11)
  • 1964: The “Council for Scientific and Industrial Research” (CSIR) assume responsibility for Astronomy in South Africa (McDowell, p.10)
  • The Republic Observatory was the time keeper for South Africa until it closed in 1971.
  • 1972 CSIR move the time standards to the National PhysicalResearch Laboratory (NPRL) (McDowell, p.10)
  • 2006: No. 18 of 2006: Measurement Units and Measurements Standards Act, 2006. Creation of Metrology Department. [Gov Gazette, 2007]



  • Bisset, W.M.: Cape Town’s Time-Guns.  Militaria 14/4 1984
  • Cape Almanac 1853-1875; Reports of HM Astronomer at the Cape of Good Hope 1879-1902
  • De Vries, G. and Hall, J.: The Muzzle Loading Cannon of South Africa, A Technical Study. HE Printers, 2001. ISBN 0-620-26902-2
  • Evans, G.: History of Time Guns and Time Balls
  • Gill, D.:  A History and Description of the Royal Observatory, Cape of Good Hope. Neill and Company, Edingburgh, 1913. ISBN 978-0-9814126-2-7
  • Glass, I.S.: The Royal Observatory at the Cape of Good Hope; History and Heritage, Megadigital, Cape Town, 2015. ISBN 978-0-9814126-03
  • Green, L.: Tavern of the Seas.
  • Kinns, R.: Time Keeping in the Antipodes: A critical comparison of the Sydney and Lyttleton Time Balls; Journal of Astronomical History and Heritage, Vol 12, No, July 2009.
  • Laing, J.D. (ed.), The Royal Observatory at the Cape of Good Hope, 1820 – 1970, A Sesquicentennial Offering, Published by The Royal Observatory, Cape of Good Hope (Cape Town), 1970. [Note: The British Science Research  Council threaten to close the observatory down. This publication was written as a Public Relations exercise to show the world the value of the institution. It was never intended to be a historical document.]
  • McDowell, M.: The National Metrology Laboratory of South Africa: the first 50 years (1947-1997)”. CSIR: Pretoria, South Africa, 2013
  • Sobel, D. and Andrewes, W.J.H.: The Illustrated Longitude, The True Story of a Genius Who Solved the Greatest Scientific Problem of His Time. LEGO, Vicenza, 1999. ISBN 1-84115-233-1
  • Warner, B.: Astronomers at the Royal Observatory, Cape of Good Hope; A history with emphasis on the nineteenth century. Balkema, Cape Town, 1979.
  • Moore, P. & Collins, P., Astronomy in Southern Africa, p.79. (General Source)
  • Vermeulen, D.J.: Living Amongst the Stars in Johannesburg“, Paarl Printing Ltd, 2006



Willie Koorts:   Cape Town’s oldest living tradition vs SA’s oldest Timekeeper

Chris de Coning:   The Origin of Scientific Study in the Southern Hemisphere – Time Signals