foreign [Music] of the celestial coordinate system let us step into certain elements of how the Indian calendaring mechanisms have been developed in this video we will understand the basic concept of a year and then we will move on to the other details in the videos to come first of all the sidereal period of an object so let us Define what is ideal period so ideal period of an object is the time taken by that particular object to complete one revolution in the background of stars for example if you take Sun then moment you say is ideal period of sun that means it went through the entire ecliptic once and came to the same position that is called as ideal period so the moon sidereal period is close to 27.32 days which constitutes one lunar cycle which means in 27.32 days it will go through that in that background of stars and that's what it means so that is called the sidereal period in the Indian system the zodiac has been divided into 27 equal parts from a fixed initial point in the ecliptic so we know what an ecliptic is so that you start from an initial Point ah that ecliptic which will make 360 degrees because after all it is a kind of a circle right so you divide it into 27 equal parts in order to trace the trajectory of the moon in the context of this because the Moon is moving really fast so you need to have several Place markers to keep track of where it is just to give you an example you know if I go from here to on on bannerghetta road which is where Indian sort of management Bangalore is if I go up to three kilometers down the line then I can put a few Place markers now I have reached you know the metro station I have reached the signal and so on the same way this ecliptic is divided into 27 equal parts ah so that the moon's trajectory can be identified where it is in the context of the Stars so e now each such division in Indian terms is called a nakshatra and since 360 degree makes it so we divided by twenty seven Three Sixty by twenty seven it will become 13 degrees and 20 minutes or if you convert everything into minutes it will be 800 minutes of an arc which forms one nakshatra and there are 27 of them so that we know where the Moon is so each division is named after a selected star that is generally prominent or traditionally well known so you know in the sky the first part of the 27 will be named after a star which is generally found there so that's how these names of the stars are also related to that space in the ecliptic and by and large the Stars the 27 divisions are equally spaced slight variations but by and large we can take it as equally spaced in the Zodiac so the full list of these 27 Stars beginning from kritika is found in thaithiriya samhita you know book 4 chapter 4 and in the 10th section slokas one two three and is also found in atharva Veda and other parts of The Vedic repository so how this ecliptic is divided you know this path on the sky is divided into 27 the 27 nakshatras are mapped also onto 12 rashes therefore each Rashi is associated with two and a quarter nakshatra so this is how this space is divided and named suitably Ah that's what it is here is the graphical picture so what you see here is those 27 Stars which are roughly divided into the 12 rashes and the point is these stars are roughly within 8 degrees on either side of this belt so to speak and the 27 stars are identified they are divided into 12 rashes and this forms the bases for keeping track of the movement of the Sun and the Moon and the other planets so that we can make our Judgment of where it is and make the necessary computations from an astronomy point of view so the entire calendaring is done based on the two luminaries in the sky namely the Sun and the Moon that's how the calendaring is done the planets are there the stars are relatively sort of stationary so in the background of that we can do it but these two luminaries sun and the moon are primarily used for calendaring purposes so the elapsed time for the sun to return to the same star which means it goes through the ecliptic one full round which is nothing but the period of revolution of the Earth around the Sun this is defined as the solar year and all solar calendars are based on this the solar calendar is followed in the states of tripura Assam Bengal Orissa Tamil Nadu Kerala and partly Punjab and haryana so these states actually follow the solar calendar then you have the period of Return of the Moon in opposition which means from Full Moon to the new moon new moon means it is in conjunction with the sun full moon means it is exactly opposite to the Sun so this one full period of either from one full moon to the next full moon or one new moon to the next new moon in uh relation to the earth that is called a lunar month and 12 such lunar months form the lunar year and this is the basis for all lunar calendars so a solar year is the basis for solar calendars and a lunar year is the basis for lunar calendars so the lunar calendar is followed in other states of India but what is interesting is in all states for fixing the dates of religious festivals for selecting auspicious time for undertaking many social religious activities and so on the lunar calendar is used therefore in some sense we may say that the Indian system is a Luni solar calendar although primarily a certain calendar is used the other calendar is also used by certain other states therefore in some sense it is a Luni solar calendar so that is how it works and this is the notion of a year and the solar and the lunar calendar which you find in in the Indian traditions we will see more details of it in the next video foreign [Music]