Fwd: Bulletin C number 70
No leap second 2025-12-31, per below. See attached patch. -- Tim Parenti ---------- Forwarded message --------- From: IERS EOP Product Center <iers.eoppc@obspm.fr> Date: Mon, 7 Jul 2025 at 05:43 Subject: Bulletin C number 70 To: <bulc.iers@obspm.fr> INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS) SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE SERVICE DE LA ROTATION TERRESTRE DE L'IERS OBSERVATOIRE DE PARIS 61, Av. de l'Observatoire 75014 PARIS (France) Tel. : +33 1 40 51 23 35 e-mail : services.iers@obspm.fr http://hpiers.obspm.fr/eop-pc Paris, 07 July 2025 Bulletin C 70 To authorities responsible for the measurement and distribution of time INFORMATION ON UTC - TAI NO leap second will be introduced at the end of December 2025. The difference between Coordinated Universal Time UTC and the International Atomic Time TAI is : from 2017 January 1, 0h UTC, until further notice : UTC-TAI = -37 s Leap seconds can be introduced in UTC at the end of the months of December or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every six months, either to announce a time step in UTC, or to confirm that there will be no time step at the next possible date. Christian BIZOUARD Director Earth Orientation Center of IERS Observatoire de Paris, France
Hi, I am not sure if this has been mentioned before but the French Annuaire pour l'an ...., publié par le Bureau de Longitudes, published annually since 1797 and available from the Gallica website, usually contains a detailed section on the legal time in France, French colonies and dependencies and elsewhere. This annual section, which of course is the most detailed for France and the French speaking part of the world with references to the appropriate official government publications, can be very useful for checking the historical references in the tz database or adding new entries. The easiest way to access these volumes is by using the weblinks at the bottom of the Wikipedia page discussing the Connaissance de Temps https://en.wikipedia.org/wiki/Connaissance_des_Temps Rob van Gent
On 2025-07-20 05:53, Gent, R.H. van (Rob) via tz wrote:
the French Annuaire pour l'an ...., publié par le Bureau de Longitudes, published annually since 1797 and available from the Gallica website, usually contains a detailed section on the legal time in France, French colonies and dependencies and elsewhere.
Thanks for the pointer. Do you happen to know which editions of "Connaissance des temps" cover legal time? That would help us cite it, by letting people know timestamps for which it might be useful. I looked at the latest edition that I could find online, which was for 2002[1], and didn't see anything to do with legal time. Thanks. [1]: https://www.imcce.fr/content/medias/publications/publications-institutionnel...
Hi, Current issues of the Connaissance des Temps do not cover legal time - much of such auxiliary material has been transferred much earlier to the Annuaire (which since 1978 has appeared under varying names). The International Meridian Conference (October 1884) is first mentioned in the Annuaire of 1886 https://gallica.bnf.fr/ark:/12148/bpt6k6541765k/f845.item From then onwards (slowly at first) lists are published of countries which adhere to the system of time zones ("fuseaux horaires") and countries which do not, like France and its colonies until 1911. A typical list from the early 1900s can be seen here https://gallica.bnf.fr/ark:/12148/bpt6k65709985/f517.item (Annuaire for 1918) Not all issues have such a list - I am slowly working though all the issues and making a list of which issues have such a time zone list. In the editions after the Second World War the time zone information is much reduced and limited to France and its colonies only. The most recent issue of the Annuaire on Gallica (2021) only lists information for France https://gallica.bnf.fr/ark:/12148/bpt6k9127672b/f52.item (with a sourced list of day light savings from 1916 to 2020) Similar lists were also published in the British and American issues of the Astronomical Ephemeris and Nautical Almanac but issues from the 20th century are much less easy to find online. Rob van Gent -----Original Message----- From: Paul Eggert <eggert@cs.ucla.edu> Sent: Monday, 21 July 2025 00:37 To: Gent, R.H. van (Rob) <R.H.vanGent@uu.nl> Cc: Time zone mailing list <tz@iana.org> Subject: Re: [tz] Annuaire pour l'an ...., publié par le Bureau de Longitudes as a useful source for historical time zone changes CAUTION: This email originated from outside of Utrecht University. Do not click links or open attachments unless you recognize the sender and know the content is safe. On 2025-07-20 05:53, Gent, R.H. van (Rob) via tz wrote:
the French Annuaire pour l'an ...., publié par le Bureau de Longitudes, published annually since 1797 and available from the Gallica website, usually contains a detailed section on the legal time in France, French colonies and dependencies and elsewhere.
Thanks for the pointer. Do you happen to know which editions of "Connaissance des temps" cover legal time? That would help us cite it, by letting people know timestamps for which it might be useful. I looked at the latest edition that I could find online, which was for 2002[1], and didn't see anything to do with legal time. Thanks. [1]: https://www.imcce.fr/content/medias/publications/publications-institutionnel...
On 2025-07-21 00:39, Gent, R.H. van (Rob) wrote:
The most recent issue of the Annuaire on Gallica (2021) only lists information for France
https://gallica.bnf.fr/ark:/12148/bpt6k9127672b/f52.item (with a sourced list of day light savings from 1916 to 2020)
Thanks for the citation. It agrees with TZDB's Europe/Paris except for spring 1923, where things were chaotic and I see some evidence that TZDB is right and the Annuaire is wrong. Perhaps someone who knows French could get to the bottom of what happened to Parisian clocks in spring 1923. In the meantime I adjusted comments to note the discrepancies by installing the attached proposed patches. The first proposed patch updates related commentary from Brazil's Divisão de Serviços da Hora (DISHO), which seems to have changed its name and acronym. The second proposed patch notes the spring 1923 disagreement between TZDB and the Annuaire and cites the New York Times report about Raymond Poincaré. I was surprised to see that the 2020 Annuaire is the current edition. Have they stopped publishing it?
Hi, The CdT en the Anuuaire are still published each year https://www.imcce.fr/publications/publications-institutionnelles/ but the most recent issues are not yet available online from Gallica. Rob van Gent -----Original Message----- From: Paul Eggert <eggert@cs.ucla.edu> Sent: Monday, 21 July, 2025 20:44 To: Gent, R.H. van (Rob) <R.H.vanGent@uu.nl> Cc: Time zone mailing list <tz@iana.org> Subject: Re: [tz] Annuaire pour l'an ...., publié par le Bureau de Longitudes as a useful source for historical time zone changes CAUTION: This email originated from outside of Utrecht University. Do not click links or open attachments unless you recognize the sender and know the content is safe. On 2025-07-21 00:39, Gent, R.H. van (Rob) wrote:
The most recent issue of the Annuaire on Gallica (2021) only lists information for France
https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgall ica.bnf.fr%2Fark%3A%2F12148%2Fbpt6k9127672b%2Ff52.item&data=05%7C02%7C R.H.vanGent%40uu.nl%7C8b9c69450b834d1133d708ddc8869278%7Cd72758a0a4464 e0fa0aa4bf95a4a10e7%7C0%7C0%7C638887202608108289%7CUnknown%7CTWFpbGZsb 3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjo iTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Ed0wQ8xVgzIA5iG3MpNxTUutr 2afgH5wGDTPChV8YkA%3D&reserved=0 (with a sourced list of day light savings from 1916 to 2020)
Thanks for the citation. It agrees with TZDB's Europe/Paris except for spring 1923, where things were chaotic and I see some evidence that TZDB is right and the Annuaire is wrong. Perhaps someone who knows French could get to the bottom of what happened to Parisian clocks in spring 1923. In the meantime I adjusted comments to note the discrepancies by installing the attached proposed patches. The first proposed patch updates related commentary from Brazil's Divisão de Serviços da Hora (DISHO), which seems to have changed its name and acronym. The second proposed patch notes the spring 1923 disagreement between TZDB and the Annuaire and cites the New York Times report about Raymond Poincaré. I was surprised to see that the 2020 Annuaire is the current edition. Have they stopped publishing it?
Hi, There is a curious history behind the erroneous date for the start of daylight saving in France in 1923 as listed in the current issues of the Annuaire du Bureau des Longitudes. In the 1924 issue, the date is given as 27 May (no hour cited). https://gallica.bnf.fr/ark:/12148/bpt6k6571678p/f265.item This is also confirmed in a short note by T. (= Émile Touchet?) in the Bulletin de la Société Astronomique de France of the same year. https://articles.adsabs.harvard.edu/pdf/1923LAstr..37..277M Then for several years (1925 - 1934) there is no "heure d'été" table. In the 1935 issue the "heure d'été" table appears again https://gallica.bnf.fr/ark:/12148/bpt6k6573371c/f212.item but with the date changed to 31 March (at 23h) and a reference to a law which was only published nearly two months later in the Journal officiel de la République française https://gallica.bnf.fr/ark:/12148/bpt6k6476007v/f4.item Apparently, when the editors decided to reinstate an "heure d'été" table for the issue of 1935, they inadvertently applied this rule to the current year while the actual start of daylight saving was not until nearly two months later on the day when the law was made public. I have not checked all issues yet but this error in the Annuaire appears to have remained unnoticed up until 1960 https://gallica.bnf.fr/ark:/12148/bpt6k9651481s/f206.item The 1961 issue https://gallica.bnf.fr/ark:/12148/bpt6k9656689b/f261.item finally has the correct date as 26 May (23h). However, this date was inexplicably changed back again to the wrong date in the Annuaire of 2002 https://gallica.bnf.fr/ark:/12148/bpt6k9645974b/f66.item and this error appears to have been unchallenged ever since. I will notify the editors of the Annuaire of this error and hopefully they will have the correct value reinstated in next year's edition. Rob van Gent
Thanks, I installed the attached proposed further commentary patch.
Hi, Another useful source for historical time zone information appears to be a series of circulars with the title "Standard Time Throughout the World" issued between 1925 and 1950 by the U.S. Bureau of Standards. I found the following issues online: Circular 280 (1925) https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular280.pdf https://catalog.hathitrust.org/Record/007291123 Circular 399 (1932) https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular399.pdf https://catalog.hathitrust.org/Record/007290917 Circular 406 (1935) https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular406.pdf https://catalog.hathitrust.org/Record/007290977 Circular 496 (1950) https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular496.pdf https://catalog.hathitrust.org/Record/007290970 Rob van Gent
Thanks for those citations; I installed the attached proposed patch.
On 2025-07-21 12:44, Paul Eggert via tz wrote:
On 2025-07-21 00:39, Gent, R.H. van (Rob) wrote:
The most recent issue of the Annuaire on Gallica (2021) only lists information for France
https://gallica.bnf.fr/ark:/12148/bpt6k9127672b/f52.item (with a sourced list of day light savings from 1916 to 2020)
Thanks for the citation. It agrees with TZDB's Europe/Paris except for spring 1923, where things were chaotic and I see some evidence that TZDB is right and the Annuaire is wrong. Perhaps someone who knows French could get to the bottom of what happened to Parisian clocks in spring 1923.
Looked up laws from 1922 and 1923; the latter is after the Spring change so the prior law should be in effect; but unsure they will be of much help: Légifrance JORF n° 0073 du 15 mars 1922 https://www.legifrance.gouv.fr/jorf/jo/id/JORFCONT000000008324 Légifrance JORF n° 0139 du 25 mai 1923 https://www.legifrance.gouv.fr/jorf/jo/id/JORFCONT000000008416 (to download you have to answer an arithmetic challenge and sometimes numbers are expressed in French words) and attach Google translated extracts of each law (fixups only to «vingt-quatre heures» times translated as 11pm! instead of 12pm) and verbatim JO extracts of each law (with OCR fixups but messy layout /sic/).
In the meantime I adjusted comments to note the discrepancies by installing the attached proposed patches. The first proposed patch updates related commentary from Brazil's Divisão de Serviços da Hora (DISHO), which seems to have changed its name and acronym. The second proposed patch notes the spring 1923 disagreement between TZDB and the Annuaire and cites the New York Times report about Raymond Poincaré.
I was surprised to see that the 2020 Annuaire is the current edition. Have they stopped publishing it?
The current annual Ephemerides for 2025 can be downloaded free, and you can buy the current releases of «Guide de données astronomiques, Annuaire du Bureau des longitudes» PDF from EDP Sciences for €12.99 (but they are not yet free from Gallica): https://laboutique.edpsciences.fr/produit/1442/9782759835959/guide-de-donnee... ToC includes «L’heure en France»: https://www.imcce.fr/content/medias/publications/publications-institutionnel... -- Take care. Thanks, Brian Inglis Calgary, Alberta, Canada La perfection est atteinte Perfection is achieved non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add mais lorsqu'il n'y a plus rien à retrancher but when there is no more to cut -- Antoine de Saint-Exupéry
Thanks, I installed the attached proposed patch to reflect the citations you found.
participants (4)
-
Brian Inglis -
Gent, R.H. van (Rob) -
Paul Eggert -
Tim Parenti