The Royal Observatory has several possible birthdays. I have, for example, seen it given as 4 March or 22 June 1675. The first is the date of Charles II’s Royal Warrant that ordered the Board of Ordnance to pay for “the support and Maintenance” of John Flamsteed, appointed “our astronomical observator” and charged
to apply himself with the most exact care and diligence to the rectifying the tables of the motions of the heavens, and the places of the fixed stars, so as to find our the so much-desired longitude of places for the perfecting the art of navigation.
The second date is that on another Royal Warrant, this time authorising the construction of the “small observatory within our park at Greenwich, upon the highest ground, at or near the place where the castle stood”. [Read more]