Star Almanack · Astronomy tools
Astronomical Clock
Civil, solar and sidereal time — and the season of the stars on your meridian.
Choose a suggested city to set longitude and time zone, or enter longitude manually below.
Default: San Bernardino, California. Change longitude for your observing location. Civil time follows the selected city, or your device time zone for manual longitude.
Live astronomical time
Civil time
Local mean solar time
Local apparent solar time
Local sidereal time
Right ascension crossing the meridian now.Meridian calendar
Approximate calendar date when this right ascension culminates at 9:00 p.m. local apparent solar time (LAT). Neighboring dates correspond to neighboring stars along the meridian.Solar and sidereal results are calculated from UTC and longitude, not from your device's displayed clock hour. Apparent solar time uses an approximate equation of time. The meridian calendar uses the 9 p.m. local apparent time culmination convention (approximately Sun RA + 9 hours).
Alarms and announcements
Use the clock above to view current astronomical time.
Automatic announcements are off by default.
Set a daily alarm by civil, local apparent solar, or sidereal time. Sidereal alarms advance about four minutes each civil day.
Alarms work only while this page is open and active. Browsers and phones may suspend background tabs, silence audio, or block speech until you interact with the page. These are not system alarms or guaranteed notifications.