The concept of time being relative in the context of special relativity does not imply that every particle is on a different timeline compared to other particles. Instead, it means that the measurement of time intervals can be different for observers in relative motion with respect to each other.
In special relativity, space and time are unified into a four-dimensional spacetime framework. The theory introduces the idea that the passage of time can be affected by relative motion and gravitational fields. Specifically, time dilation and length contraction occur when objects are moving relative to each other.
However, within a particular reference frame, particles experience time in the same way. If two particles are at rest relative to each other, they will measure time in the same manner. Similarly, particles that are interacting with each other will experience time in a consistent manner within their shared reference frame.
It's important to note that the concept of different timelines for particles is not a consequence of time relativity in special relativity. The theory provides a framework for understanding the behavior of time and space, but it does not suggest that particles have separate timelines or exist in completely separate temporal dimensions.