Events in event sourcing hold actual change from the past. This means the sequence of events could be treated as a factual history.
A factual history is something that does not change, and of course happened in the past.
Reference
Hoffman, Kevin. Real-World Event Sourcing: Distribute, Evolve, and Scale Your Elixir Applications. The Pragmatic Bookshelf, 2025. The Pragmatic Programmers.
Highlights or timestamps
Every event represents something that actually happened.
— highlight from Highlights of Real-World Event Sourcing
Event Sourcing is all about deriving meaningful state from the past.
— highlight from Highlights of Real-World Event Sourcing
All events are Immutable and Past Tense.
— highlight from Highlights of Real-World Event Sourcing