Here’s a crucial tool for every D4 player out there. World Bosses are a great way of getting legendaries and even uniques, and the in-game notification system is not good. Luckily, Prowner1 has created a site where you can see if there’s a World Boss up (or even a Helltide or Legion event)!
The site works off of live player reports so you can see if an event is up. However, you can also pretty clearly see when the next World Boss is coming up. There seems to be a 5 and a half hour gap between them at the moment.
So you just have to be around when the next one should pop up, and then check the site to see which one it is! Hopefully this helps you out in the search for those big loot pinatas. You can click here to head to the site.