When a security analyst needs to filter events based on the time they occurred on the endpoints, the most relevant parameter to use is "Log Source Time." This parameter reflects the original timestamp of an event as recorded by the log source, providing the actual time when the event took place on the endpoint, regardless of when the event was received or processed by QRadar. This is crucial for accurate temporal analysis of events, ensuring that the timing of activities is correctly aligned with the actual occurrence on the devices or systems generating the logs.