One full Neptune-year, which lasts 164.79 Earth-years, has now passed since its discovery. Figuring out the exact timing of this milestone is surprisingly complicated – it depends on the uncertain time of the discovery, and on exactly how you define "one Neptune orbit", since there are slightly different ways to do that.
Last week saw Neptune Day, the first anniversary - in Neptune years - of the planet's discovery on September 23, 1846. That got us thinking: what are the "birthdays" for all the other planets? Here's a handy, mildly insane guide.