Key historical events that UPSC candidates should be aware of include significant milestones within Indian history, such as the freedom struggle, socio-reform movements, and independence, as well as global events that shaped the modern world. Familiarity with important political developments, economic reforms, and the evolution of social policies is critical for a comprehensive understanding of contemporary issues. Additionally, events like the formation of the Indian Constitution or major international conflicts illustrate the interplay between history and current affairs. Such knowledge aids in contextualizing questions across various examination papers.