Find out how many days, months and years there are between any two dates.
Add or subtract any number of days to/from a start date.
Find out the precise duration between two dates and times of day — down to the second.
Add or subtract days, hours, minutes, and seconds to/from a start date and time.
Day length, azimuth, distance etc.
Equinoxes and Solstices mark the beginning of a new astronomical sesason. Local dates and times.