As the sun sets in the west darkness rises from the east. what is the time difference between two scenarios?

Question

For e.g. if sun sets at 7 pm, the darkness starts spreading immediately. Do both the phenomena occur at exactly the same time or there is any difference of 2, 5,10 or 15 minutes between both. Or in other words if one says, "we will meet at the time when the sets in the west and the darkness rises from the east" what time (or time span) will this sentence reveal

Answer 1

In fact darkness should appear as soon as the sun sets in.But scattering of the sun's light by the atmosphere extends the day time by some more minutes.The time delay depends upon the weather conditions of the atmosphere at that time over that place.

Answer 2

The interim period between sunrise and full light (or full light and darkness) is known as twilight. Depending on the location, it can last different periods of time. Today in my location, sunrise will be at 5:20 a.m., but civil twilight starts at 4:41 a.m.; likewise, sunset will be at 9:06 p.m., but civil twilight will continue until 9:45 p.m.

Answer 3

12 hours