Today, according to Wikipedia, is the Grand Duke’s Official Birthday in the Grand Duchy of Luxembourg. Wikipedia explains, in text made available under the usual Creative Commons Attribution-ShareAlike License 4.0, “It is celebrated on 23 June, although this has never been the actual birthday of any ruler of Luxembourg.… The monarch’s birthday has not always been celebrated on 23 June. Under William I (1815–1840), the date was 24 April (although his actual birthday was 24 August), and under William II (1840–1849), it was 6 December, his actual birthday. Because William I abdicated between 24 April and 6 December, the holiday was celebrated twice in 1840. Under William III (1849–1890), the date was set at 17 June until 1859, after which his birthday was celebrated on 19 February, two days after his actual birthday.”
We’re only about halfway to the final choice of June 23, but you’ll have to read the rest of the article at the source.
So happy birthday to you, Grand Duke Henry/Henri/Heinrich, and Dr. Boli really has no more to say on that matter.
By the way, did you know that the national motto of Luxembourg is “We want to stay what we are”? No other state that Dr. Boli can remember has ever adopted the law of conservation of mass so enthusiastically.