Time and location
Time travel, location and sidereal time
The sky depends on where and when you observe. Apphemeride calculates it for locations around the world and the time you choose, with local sidereal time shown alongside.
- What will the sky look like on a trip to the Grand Canyon?
- Where was the Moon on my birthday?
- How does observing from a mountain affect sunrise?
Time travel
Choose a date, move through time with the time control or jump straight to an event. In live mode, the view updates every second.
Your location
Use GPS, address search or coordinates, together with the selected location’s time zone.
Observer elevation
From a mountain or aircraft, the visible horizon is lower. Enter your elevation so the app can account for horizon dip in rise and set times.
Local sidereal time
Sidereal time in the location bar tells you which right ascension is crossing your local meridian.
Live time, GPS location and local sidereal time are free. Time travel, address search, coordinates and observer elevation are part of the full version.
Frequently asked questions
Which time zone does the app use?
Your iPhone’s time zone or that of the selected location.
Why does elevation affect sunrise?
From a higher viewpoint, the visible horizon dips below eye level, so the Sun appears earlier and disappears later.
What is sidereal time?
Time measured by Earth’s rotation relative to the stars. A sidereal day lasts about 23 hours and 56 minutes.
Download Apphemeride
Free to download. The Sun and Moon are always free. Unlock the remaining features with the full version: a one-time purchase after a three-day trial, with no subscription.
