With the passing of days, weeks, months, years, decades, centuries, and millennia we time-stamp life, and so assume we are moving forward in a linear fashion.
Ponder the fact that, every single day we actually go around the sun. The sun does not actually rise in the morning or set in the evening - we move around the sun - day after day, millennia after millennia. It is only our position in relation to the sun, that determines whether we are experiencing Summer, Autumn, Winter or Spring.
So, if we are cycling around and around the sun, then we continuously move back to the same point, every day. This is a simple truth, but something we don’t stop to reflect on. As each day passes by, we make it our ‘past’, as we move to the next.