Tirhuta Panchang

Tirhuta Panchang (Devanagari: तिरहुता पंचांग, Tirhuta: 𑒞𑒱𑒩𑒯𑒳𑒞𑒰 𑒣𑓀𑒔𑒰𑓀𑒑, IPA: "Tirhutā pan̄cāṅg") is a calendar followed by the Maithili community of India and Nepal. This calendar is one of the many Hindu calendars. It is a tropical solar Hindu calendar in which the year begins on the first day of Baishakh month i.e. Mesh Sankranti. Every year, this day falls on 13/14 April of the Gregorian Calendar.
Pohela Boishakh in West Bengal, Bohag Bihu in Assam, Puthandu in Tamil Nadu, and Vaisakhi in the Punjab region are observed on the same day. These festivals also mark the beginning of the New Year in their respective regions.
Months.
Names and approximate lengths of Maithili months :
Months and their corresponding season.
Baisakh-Jeth-Asarh.
These three months are the summer season in Mithila, out of these 3, Jeth & Asarh are very hot. Baisakh is the month of Litchi. Jeth and Asarh are the months of Mango.
Saon-Bhado.
Mithila receives heavy rainfall during these two months, often resulting in flooding. Farmers wait for saon's first rain so they can sow paddy in their fields. The holy month of Saon is devoted to Lord Shiva. Devotees visit Baidnath Dham in Deoghar to offer gangajal.
Asin-Katik.
These two months have moderate weather. Both these months are festive season for Mithila. Navaratra falls in Asin, Diwali & Chhath Falls in Katik. Moreover, Katik is the harvesting month for farmers.
Agahan-Poos-Magh.
Agahan, Poos and Magh are the winter seasons in Mithila. Out of these 3, Pous & Magh are the extreme winter periods, temperature sometimes falls to 5 °C. Makar Sankranti falls in the month of Pous, and vasant Panchami in Magh.
Fagun-Chait.
After winter, Fagun & Chait are the moderate months. Fagun & Chait again are the harvesting months. Holi falls in Fagun and Chhath falls in Chait. Chaith is the last month of Maithili Calendar.
Days in Maithili calendar.
Like, most of the calendars of the world, Maithili calendar also has 7 days in a week, each of 24-hour length. Ravdin or Sunday is supposed to be the first day of the week.
Significance.
The Maithili calendar is the calendar of Mithila which originated in Mithila region. The Maithili calendar is of great importance for Maithil people in India as well as in Nepal. All auspicious dates (e.g. marriage, "Mundan", "Upanayana sanskar") as well as the dates of Maithili festivals (e.g. Dipawali(Diwali/Tihar), "Chhath", Durga Puja, Janaki Navami") are set based on the Maithili calendar. It has deep roots in the Hindu religion and Mithila's culture.
Related calendars.
The Maithili calendar is related to the Hindu solar calendar, which is itself based on the Surya Siddhanta. The Hindu solar calendar also starts in mid-April, and the first day of the calendar is celebrated as the traditional New Year in the Indian states of Assam, West Bengal,Kerala, Manipur, Orissa, Punjab, Tamil Nadu, and Tripura. Bangladesh, Nepal, Thailand and Sri Lanka also celebrate new year around the same time (13–15 April). This day is also known as "Mesha Shankranti".