solar calendars

Solar calendars are calendars built around Earth's yearly journey around the Sun, keeping their year synchronised with the cycle of seasons.

• The widely used Gregorian calendar is a solar calendar — its months are adjusted so the year adds up to 365 days, which is why some months run 30 days, others 31, and February just 28.
• Because Earth actually takes slightly more than 365 days to orbit the Sun, solar calendars add an extra day every four years — a leap year — to stay lined up with the seasons.
• Knowing when seasons would arrive mattered enormously for agriculture, which is exactly the practical need that drove the creation of solar calendars in the first place.
• India's own national calendar is also a solar calendar, beginning each year on 22 March (the day after the spring equinox) and using traditional Indian month names.