If one reverses this motion, it is clear that ALL of the matter in the visible Universe was located in a very dense concentration roughly 13 billion years ago.

https://www.e-education.psu.edu/astro801/content/l10_p5.html

You can actually calculate an estimate for the age of the Universe from Hubble's Law. The distance between two galaxies is D. The apparent velocity with which they are separating from each other is v. At some point, the galaxies were touching, and we can consider that time the moment of the Big Bang. If you take the separation between the two galaxies (D) and divide that by the apparent velocity (v), that will leave you with how long it took for the galaxies to reach their current separation. The standard analogy here is to consider that you are now 300 miles from home. You drove 60 mph the entire time, so how long did it take you to get here? Well, 300 miles / 60 mph = 5 hours.

So, the time it has taken for the galaxies to reach their current separations is t=D/v
.
But, from Hubble's Law, we know that v=H0D
.
So, t=D/v=D/(H0×D)=1/H0
. So, you can take 1/H0
as an estimate for the age of the Universe.
The best estimate for H0=73km/s/Mpc
. To turn this into an age, we'll have to do a unit conversion.
Since 1Mpc=3.08×10¹⁹km
, H0 = (73 km/s/Mpc) x (1 Mpc/3.08 x 10¹⁹ km) = 2.37 x 10⁻¹⁸ 1/s
.
So, the age of the Universe is t = 1/H0 = 1 / 2.37 x 10⁻¹⁸ 1/s = 4.22 x 10¹⁷ s = 13.4 billion years
.