An interesting week for anniversaries this week. On Monday it was the anniversary of the 1921 truce between the IRA and the British Government in the Irish War of Independence. Of course, that was not quite the end of the trouble and on Tuesday, the (Northern) Irish celebrated Orangemen's Day when they annually try to re-start the war, in commemoration of the Battle of the Boyne, although it's not quite so clear these days what they hope to gain from it. We have Bastille Day tomorrow, which triggered the French revolution in 1789 - and the French remain bloody awkward. Friday brings the anniversary of the Greek Junta/CIA sponsored coup d'etat against Makarios in Cyprus in 1974, which led to the Turkish invasion and so forth.
But more significantly, in cosmological terms, we have the first Neptunian anniversary of the discovery by Earthmen of the planet Neptune. That is, although Earthmen discovered Neptune in 1846, it is only one year, or orbit of the sun, so far as Neptune is concerned. (Apparently, Galileo had seen Neptune some years before but thought it was a star rather than a planet.) Since the recategorisation of Pluto as a dwarf planet in the Kuiper Belt, Neptune is the outermost planet in Earth's solar system.
More info at the redoubtable BBC.