On 2020-06-09 20:52, Paul Eggert wrote about strange jumps in tzdb time scales:
There are other such cases in tzdb. For example, the 1911-03-11 transition in Paris is from 00:01 Paris Mean Time to 23:51:39 GMT the previous day. If the comments are right this transition came from Ciro Disceopolo but we don't have exact citations.
Well, that is what tzdb says, but what actually happened was different, and it was the same in Paris and in Monaco. Le Gaulois, 1911-03-11, page 1/6, online at [https://www.retronews.fr/societe/echo-de-presse/2018/01/29/1911-change-lheur...] "Instantanément, toutes les horloges pneumatiques s'arrêtèrent... Neuf minutes vingt et une seconde plus tard, les aiguilles reprirent leur marche circulaire." [ Instantly, all pressure driven clock dials halted... Nine minues and twenty-one seconds later the hands resumed their circular motion. ] There are also precise reports about how the change was prepared in train stations: all the publicly visible clocks stopped at midnight railway time (or were covered), only the chief of service had a watch, labeled "Heure ancienne", that he kept running until it reached 00:04:21, when he announced "Heure nouvelle". See the "Le Petit Journal 1911-03-11", online at [https://gallica.bnf.fr/ark:/12148/bpt6k6192911/f1.item.zoom]. Anyway, thanks for your remarks! Michael Deckers.