5) The Ancient Indian calendar

It is traditionally known as “panchanga”. It is based on the lunar cycle. A day is measured as the time between one sunrise and the next.  Similarly, a month is the period from one moon cycle to the next. A lunar month lasts 28 days. A year is measured from the beginning of a season until its return. A lunar year lasts 12 months or 254 solar days.  An additional month known as “adhika” is added to the calendar at five-yearly intervals as a lunar year falls short of a solar year by 12 days. Each month is divided into two cycles of the moon (new moon to full moon and back). There are 4 seasons in a year and a season is known as “rtu”. Today, there are several regional Indian calendars as well as Indian National calendar.  Some of these are the Bengali calendar, Nepali calendar, Tamil calendar  and Kannada calendar.