AÂ solar calendarÂ is aÂ calendarÂ whose dates point
the position of the earthÂ on its revolution around theÂ sunÂ or
equivalently the apparentÂ position of the sunÂ moving on theÂ celestial sphere.
- the Earth’s orbit around the Sun on a tilted axis causes the Sun to appears to gradually rise and fall in the sky during the year – this effect causes the `midnight sun` phenomenon that is experienced at high latitudes near the poles.
- solstice – point at which the Sun appears to stop rising or falling and stands still in the sky.
- summer solstice – happens on 21st June, marks the Sun’s most northerly extension above the Equator – at 12 noon on 21st June the Sun is directly overhead at the Tropic of Cancer.
- winter solstice – happens on 21st December, marks the Sun’s most southerly extension below the Equator – at 12 noon on 21 December the Sun is directly overhead at the Tropic of Capricorn.
- equinox mean “equal night” marks both the time time and place at which the Sun cross the equator – during an equinox, everywhere on the planet has exactly 12 hours of daylight and 12 hours of darkness.
- Spring equinox – on around 21st March every year – the spring equinox happens – marks when the Sun crosses the Equator from south to north.
- Autumn equinox – on 23rd September every year – the autumn equinox happens – marks the Sun crossing the equator from north to south.
- vernal equinox – using as the zero point in the celestial co-ordinate system.
Solstice and Equinox