The Panjika (IAST: Pañjikā; Assamese: পঞ্জিকা; Bengali: পঞ্জিকা; Maithili: পাঁজিক, पाँजिक; Nepali: पञ्जिका; Odia: ପଞ୍ଜିକା) is the Hindu astronomical almanac, published in Assamese, Bengali, Maithili, Nepali and Odia languages and colloquially known as Panji (IAST: Pāñji; Assamese: পাঁজি; Bengali: পাঞ্জি; Odia: ପାଞ୍ଜି). In other parts of India it is called panchangam.

There are two schools of panjika-makers in Bengal – Driksiddhanta (Bisuddhasiddhanta Panjika) and Odriksiddhanta (Gupta Press, PM Bagchi, etc.). They dictate the days on which festivals are to be held. Sometimes, they lay down different dates for particular festivals. For the Durga Puja in 2005, two different sets of dates came through. Some community pujas followed the Gupta Press Panjika, because of its popularity. With deference to convention, it confirmed Pandit Nitai Chakraborty, president of Vaidik Pandit O Purohit Mahamilan Kendra. Belur Math adhered to Bisuddhasiddhanta Panjika. Swami Vijnanananda (who became Math president in 1937–38), an astrologer, decided that Ramakrishna Mission would follow this almanac as it was more scientific.

The difference occurs because the two schools follow different calendars of luni-solar movement on which tithis are based. While Gupta Press Panjika follows 16th century Raghunandan's work Ashtabingshatitatwa based on the 1,500-year-old astronomical treatise, Suryasiddhanta. Bisuddhasiddhanta Panjika is based on an 1890 amendment of the planetary positions given in Suryasiddhanta.

The earliest Indian almanacs date back to around 1000 BCE. It did analyse time but the calculations were not always very accurate. Suryasiddhanta, produced in that era, was the forerunner of all later day panjikas.

During British rule, Biswambhar again began the work of publishing the panjika, in handwritten book form. The printed version came in 1869. Bisuddhasiddhanta Panjika was first published in 1890. Gupta Press follows Suryasiddhanta with the original format while the version with "corrected" scripture is called Visuddhasiddhanta.

The Bisuddhasiddhanta Panjika came into being because an astronomer Madhab Chandra Chattopadhyay, on studying the panjikas then in vogue found differences in the actual and astrological position of the planets and stars. He revised the panjika as per scientific readings. There were other people in different parts of India who also supported the approach for scientific revision of the panjika. It included such people as Pathani Samanta in Odisha and Bal Gangadhar Tilak in Pune.

In 1952, a major revision of the panjika was undertaken under the aegis of the Indian government.

Gupta Press, one of the Bengali panjikas, has come out in 2007 with a CD-version packed with interactive features like 'know your day', 'daily horoscope' and 'koshthi bichar' (horoscope). Transformation has been staple food for the panjika. With the passage of time it has added information, like tourist attractions, pilgrim destinations, telephone codes and general information that common people seek, to make it more attractive. The format has also been made more flexible to cater to the needs of varied groups. The variants like 'directory panjika' (magnum opus) 'full panjika' (thinner version) and 'half panjika' (abridged version) and 'pocket panjika' have different price tags. The pocket panjika is a hawkers' delight on local trains.