Diablo 4's nature as a live service game means that players have since launch been trying to work out how it handles recurring events: when and where the world bosses spawn, when helltides are due to occur, and the same for legion events. A rough consensus formed pretty early, but now they've only gone and blown the bloody doors off.
A player called Shalzuth recently posted the fruits of their labours to the Diablo 4 subreddit, claiming to have worked-out (with help) the spawn times for all the above: to the extent they've now got a section of a popular Diablo 4 site with countdown timers and maps for each.
