Since the Sun does not "move" relative to the rest of the solar system, sunrises and sunsets are created by either the movement of the Earth or the movement of astronauts around the earth while in orbit. An astronaut could see the sun "rise" and "set" in a 90 minute cycle.
But for those of us, less fortunate, with feet on the ground of good ole Mother Earth, we have to wait for the rotation of the Earth on its axis to generate our sunrises and sunsets. There, you may have a way of saying that you've seen "two" sunsets in "one" day.
After the summer solstice in June (northern hemisphere) or in December (southern hemisphere) the days begin to get shorter and the amount of daylight less. This continues until the winter solstices when days begin to get longer. While the days are shortening, sunsets (and sunrises) begin to take LESS than 24 hours to happen. For instance, in November, where I live, sunset occurred at 5:13pm. Each day afterward, for the next week, the sun set about a minute earlier or 23 hours and 59 minutes later. Technically, that could be considered two sunsets in one "day" of 24 hours, but on the non-technical side, you'll never see the sun set at 10am, rise at noon, then set again at 5pm. That would require some motion in the Earth that will never happen naturally.
