SciencePrehistoric (c. 10,800 BCE)global (Northern Hemisphere)high confidence

The Younger Dryas began at the end of the last Ice Age, approximately 12,800 years ago.

Notes on verification

Multiple independent scientific and encyclopedic sources, including peer-reviewed ice core data, consistently place the Younger Dryas onset at approximately 12,800-12,900 years ago, corroborating the claim. [cascade flags: aggregator_dropped_primary_exists | tier=silver indep_score=0.925 clusters=2 claim_tier=everyday]

Sources