Astronomical Times Calculator

Date and time =
Timezone (hrs) offset from GMT =
Longitude east of GMT =
Local sidereal time =
Julian Day =


Shows relationship between datetime, timezone and Julian Day; as well as Julian Day, longitude and sidereal time.

Both time zone and longitude are positive when east of the prime meridian and negative when west. For instance, the USA has negative timezones and negative longitudes.

Sidereal time and Julian Date are calculated from the input datetime and longitude and the computer's timezone.
Datetime is calculated from the input Julian Date and timezone. Longitude and local sidereal time are ignored.

Mel Bartels