In every area the sun rises and sunsets at different times based on the time zone, technically the sun does rise when it's 18 degrees below the horizon.
Astronomical dawn: the moment after which the sky is no longer completely dark; formally defined as the time at which the sun is 18 degrees below the horizon in the morning.
But this does not mean the chart is accurate based on your area. The chart should have variation depending on where you live, otherwise its not accurate since the sun rises and sets at different times in different areas based on when it's located 18 degrees below the horizon.
A better way to calculate is, to use a calculator in which it varies based on where you live and puts into account the mathematical definition of sunrise and sunset, the chart you provided has an option to use the degree rule, so it can be used if you want it based on your area and the degree rule.
Sources: Wikipedia article of Dawn