The 'অসমীয়া কেলেণ্ডাৰ' (Assamese Calendar) is an integral part of Assamese culture, deeply rooted in ancient astronomical traditions and primarily a solar sidereal calendar. Its history traces back to the widely adopted Indian calendar system known as the Saka Era (Shaka Samvat), which began in 78 CE. While the foundational principles are shared with other Indian calendars, the Assamese calendar has evolved with distinct cultural interpretations and usage within Assam and its diaspora. It is based on the Surya Siddhanta, an ancient Indian astronomical treatise, which governs the calculation of planetary positions and time.
Culturally, the Assamese Calendar holds immense significance. It is the backbone of all traditional festivals, rituals, and auspicious timings for the Assamese people, predominantly in the state of Assam in Northeast India. The most prominent festival dictated by this calendar is Bohag Bihu (also known as Rongali Bihu), which marks the Assamese New Year. This vibrant festival, celebrated with immense fervor, symbolizes the onset of spring and the sowing season. Other significant festivals like Kati Bihu and Magh Bihu, as well as various religious ceremonies, marriages, and agricultural activities, are all scheduled according to this calendar. It serves as a cultural anchor, connecting generations to their heritage and traditional way of life.
In practical usage today, the Assamese Calendar operates alongside the Gregorian calendar, particularly for cultural and religious purposes. Its structure is based on the Sun's transit through the sidereal zodiac, giving it twelve months. The month names, derived from Sanskrit and corresponding to zodiac signs, are: Bohag (Mesha), Jeth (Vrisha), Ahar (Mithun), Sawan (Karkat), Bhada (Singha), Aahin (Kanya), Kati (Tula), Aghon (Vrischika), Puh (Dhanu), Magh (Makar), Phagun (Kumbha), and Sot (Meen). The New Year, as mentioned, is determined by the Sun's entry into the sidereal Aries (Mesha Sankranti), which typically falls around April 14th or 15th of the Gregorian calendar. Weekday names are similar to those used across India, derived from celestial bodies: Robibar (Sunday), Sombar (Monday), Mangalbar (Tuesday), Budhbar (Wednesday), Brihaspatibar (Thursday), Shukrabar (Friday), and Shanibar (Saturday). Unique features include its sidereal nature, meaning months are fixed relative to the stars rather than the equinoxes, and its use in Assamese 'Panjikas' (almanacs) which provide detailed information on 'tithi' (lunar day), 'nakshatra' (lunar mansion), and auspicious times for various events, making it indispensable for daily life and cultural practices.