What is the approximate age range associated with ancient globular clusters?

12 to 13 billion years ago.

Globular clusters are ancient, tightly bound groupings of hundreds of thousands of stars that represent some of the oldest stellar populations observable in the universe. Dating methods, particularly analyzing the main-sequence turnoff point on their color-magnitude diagrams, consistently place the formation time for these systems in the early history of the cosmos. The established estimate derived from these observations indicates that these ancient collections formed approximately 12 to 13 billion years in the past. Because these stars are nearing the very end of their main-sequence lifetimes, even minor differences in their age result in significant, observable positional shifts on the CMD, allowing for relative precision despite their immense absolute age.