Some map-marked Dragon Isles rares outside elite areas follow a timed rotation. Blizzard's Dragonflight patch 10.0.5 notes changed their cadence from two spawns every two hours to one every 30 minutes. This change applied to some rares, not every rare creature on the islands.

For upcoming spawns, check the Timed Dragon Isles Rares panel on Wowhead's live WoW Retail page. Its live schedule is a better starting point than the fixed spreadsheet shown here.

The image shows the community spreadsheet used when this rotation was first mapped. Use it as background, and check the live schedule before heading to a spawn location.