By Laba Lal Pradhan Lunar calendar was developed first by the experience of human naked eye. There is a gap of about 30 days from oneaunshi  (new moon) to next aunshi, This gap of about 30 days  was counted as a month in the lunar calendar. They also discovered that the moon returns tothe  same part of the  group of stars after 12 aunshis, which made a year   But there were only 354 days  in a year. Many years after the introduction of lunar calendar the scientist proved that earth goes round the sun in 365 days. This period wasdefined as a year. Thus there was a difference of 11 days in the lunar and solar calendars.  For adjusting this deficit of 11 days a year, they added one extra month in every three years.  This extra month is known as purusotammahina in BikramSambat and analamahina in Nepal Sambat. All calendars have basic day, month, year and new year day.  A day in the lunar calendar practiced by Nepal Sambatstarts from the rising sun and ends in next rising sun instant, which is traditionally of 60 ghadis. And from the next day of aunshicalled pratipada to the next aunshi was called a month, which  may be of  29 or 30 days. The new year day of Nepal Sambad is fixed on the day of Mahapuja when the sun is on thelibra zodiac and moon is just afteraunshi that kachhalathopratipada. From one aunshi to next aunshiis divided into 30 equal angles in the sky called 30 tithies. But entering of the moon on any tithi does not lie in the same time. Any tithi may start from morning, day, evening or night. So it is 24-hour variable. Things based on fixed thing and anything developed on this fixed thing are practically applicable and spreads all over the world. So Greenwich time is taken basis to fix time of any place.  So is time fixed from rising sun instant in the lunar calendar. Start of tithi being variable, our ancestors took the fixed point rising sun instant tithi for the whole day. In lunar calendar there is no gate or tarikh, it simply has day(bar) and rising sun tithi. So for practical use all the festivals were fixed according to morning tithi day. That was more practical and scientific when it was introduced. But nowadays panchang worker changed this basic idea. They fixed the festival day according to when puja is to be done. For morning puja morning tithi, for day puja day tithi, for evening puja evening tithi was selected, which is not practical and scientific, because a tithi is divided into two days. They mark Krishnasthami on Saptami day, but Krishna Rathyatra is done next day. Was Krishna born on two days? BikramSambat Bikramsambat is the mixture of the lunar calendar and solar calendar, where tithi is used for  thereligous activities and festivals and gate as solar calendar is used in official works.  Months are fixed on the basis of the zodiac signs on which the sun lies.  It hasthus  two new year days Baisakh Krishna Pratipada as lunar new year and Baisakh 1 gate as solar new year day, which our nation celebrates. But it has drawback,  days of every month varies year by year, it may be 29,30,31,32 days. Due to this variables, monthly data are not standard, not reliable , it never 100% success according to these data.. So for technical basis we should have fixed days month. Because of this drawback, BikramSambat months are not in use in embassies, organizationsdealing with foreign countries and replaced by Gregorian date. For counting number of days in interest calculation in banks are done by Gregorian calendar. Gregorian calendar date is demanded in passport and citizenship certificates. So our calendar must have fixed days month system and it must be easy to convert in Gregorian date. New Nepal sambat solar calendar Hence our calendar should be connected with lunar calendar with fixed days and month. But one thing is sure that Gregorian calendar cannot be used because it does not have any connection with lunar calendar. But Nepal Sambat being lunar calendar only need to take some features of the solar calendar so that it can replace BikramSambatfrom the land of its origin—Nepal. Such new solar calendar for Nepal Sambatis proposed here for the year 1137 nepalsambat.Mhapuja lies between Octber 19 to November 16. Kachhala30 days (Karunamayala, 1st ta coincide with 31stOctobar) Thila31 days (bright sun month) Pohela 30 days (snow and hail pouring month) Silla30 days and in leap year ie year exactly divisible by 4 will be 31 days (smallpox goddess sitalamayila) Chilla  31 days (Chirswayegula, fagu) Chola  30 days (Jamachola, its Purnima is fixed for visiting Jamacho)Balaju fair also. Bachhala  31 days (Bikramsambat first month) Tachhala  31 days (Tathagat first month) Dela 30 days (nation economical important month) Gunla  30 days (ancestor remembrance month) Yanla  31 days (Indrajatra month) Koula 30 days (Dashain,Monila) The 2nd(thila),5th(chilla),8th  (tachhala) and11th (Yanla) months are of 31 days ,which are shortest day month, longest day month,and two day and night equal month. Bachhala is made 31 days month instead of Kachhala. Silla is the leap year month (30days changes to 31 days in leap year) Date as gate in Bikramsambat will be called ta in new Nepal sambat solar calendar All Nepalis in the world can construct this calendar themselves. Not only that he can convert tarikh to ta and vice versa and by the name of the month he can be able to know the climate condition of the coming festival in that month.