On iOS, astronomy apps tend to be about gazing from Earth to the heavens, butCosmic-Watch instead has you peering at the Earth and explore its relationship with time and the cosmos.
The default view is a clock that surrounds the planet like Saturn’s rings. You can pinch and drag to zoom and spin the planet, and the app enables you to save multiple locations to snap to via a tap. Elsewhere, you can overlay constellations and astral charts, and experiment with a digital model of the solar system.
A neat additional feature is time travel. Tap the clock icon and you can fast-forward your view. This is particularly lovely in the model, which when running sufficiently quickly (say, a month per second) leaves wiggly trailing paths from planets as they make their way around the sun.