Our lives are divided, in terms of time, according to the movement of astronomical objects. Earth’s rotation on itself and around the Sun creates the basis for our days and years, but our movement around the galaxy is not really celebrated.

To take care of this, a group of science enthusiasts has launched Galactic Tick Day, which falls later this month on September 29. Obviously, a loop of the Milky Way is not a human-friendly time, so the minds behind the project picked a small fraction of the 225 million years it takes the Sun to complete a full galactic orbit.

The team looked at the most appropriate fraction of time. The Sun’s orbit is circular enough that it can be divided into 360 degrees, but each degree is still hundreds of thousands of years. The degree, however, has subdivisions that can be divided into 60 parts – the arcminutes – and each arcminute can also be divided into 60 arcseconds. This is still beyond the human lifespan, so they picked a smaller interval by dividing the arcsecond by 100.

That means Galactic Tick Day happens every 633.7 Earth days, corresponding to one centi-arcsecond (about 0.0000077 percent) of the full orbit. This newly establish event has the arbitrary start date of October 2, 1608, the day Hans Lippershey patented the first telescope. This latest event would be the 235th Galactic Tick Day.

Although this event is not officially sanctioned in the calendar, it is an interesting reminder that our days and years are just the quick tick of a much larger cosmic clock.