No, we do not have an absolute reference point for time. Our best models of physics are time-translation symmetric (this is equivalent to conversation of energy

No, we do not have an absolute reference point for time. Our best models of physics are time-translation symmetric (this is equivalent to conversation of energy via Noether's theorem), so absolute time cannot have any measurable effect. There is, however, a human made reference time scale (International Atomic Time, TAI) which is generated by the BIPM using (mostly GPS-based) comparisons of the local time scales of many national labs.