Today is the Bengali New Year, 1421, so Shubho Nobo Borsho from Tarikh Par Tarikh!
The Bengali Calendar, introduced by Mughal Emperor Akbar, has an interesting history. Here is an excerpt from Amartya Sen’s Argumentative Indian on the topic:
Akbar's attempt at introducing a combined calendar paralleled his interest in floating a combined religion, the Din-ilahi. On the calendrical front, Akbar may have begun by just taking note of various calendars (Hindu, Parsee, Jain, Christian and others), but he proceeded then to take the radical step of trying to devise a new synthetic one. In 992 Hijri (1584 CE, Gregorian), just short of the Hijri millennium, he promulgated the brand new calendar, viz. the Tarikh-ilahi, God's calendar - no less. The zero year of Tarikh-ilahi corresponds to 1556 CE (the year in which Akbar ascended to the throne), but that is not its year of origin, which was 1584. It was devised as a solar calendar (like the Hindu and Iranian/Parsee calendars of the region), but had some features of the Hijri as well, and also bore the mark of a person who knew the calendrical diversity represented by Christian, Jain and other calendars in local use in Akbar's India. The Tarikh-ilahi became the official calendar, and the decrees of the ruling Moghal emperor of India (the farmans) henceforth carried both the synthetic Tarikh and the Muslim Hijri date, and occasionally only the Tarikh.
Even though Tarikh-ilahi was introduced with a grand vision, its acceptance outside the Moghal court was rather limited, and the subcontinent went on using the Hijri as well as the older Indian calendars. While Akbar's constructive calendar died not long after he himself did, his various synthesizing efforts left a lasting mark on Indian history. But has the calendrical expression, in particular, of Akbar's synthesizing commitment been lost without trace?
Not so. There is a surviving calendar, the Bengali San, which was clearly influenced by Tarikh-ilahi, and which still carries evidence of the integrating tendency that is so plentifully present in many other fields of Indian culture and tradition (such as music, painting, architecture, and so on). It is year 1407 now (as I write in 2000 CE) in the Bengali calendar, the San. What does 1407 stand for? Encouraged by Akbar's Tarikh-ilahi, the Bengali calendar was also 'adjusted' as far as the numbering of year goes in the late sixteenth century. In fact, using the zero year of the Tarikh, 1556 CE (corresponding to year 963 in the Hijri calendar), the Bengali solar calendar, which has a procedure of reckoning that is very similar to the solar Saka system, was 'adjusted' to the lunar Hijri number, but not to the lunar counting system. That is, the 'clock' of this solar calendar was put back, as it were, from Saka 1478 to Hijri 963 in the newly devised Bengali San. However, since the Bengali San (like the Saka era) remained solar, the Hijri has marched ahead of the San, being a lunar calendar (with a mean length of 354 days, 8 hours and 48 minutes per year), and the Bengali San - just turned 1407 - has fallen behind Hijri as well.
This (somewhat complicated) combination of the lunar Muslim Calender and the solar Hindu system means that every Bengali year references two events: One, the Hijra or the migration of Prophet Mohammad from Mecca to Medina, which is the year 1 of both the Islamic as well as the Bengali Calendar. The other event the Calender references is Akbar’s coronation, at which point the Mughal Empire retrospectively changed its official calendar from Islamic (lunar) to Akbar's own Tarikh-ilahi (solar).
The “formula”, as it were, for calculating the Bengali year, therefore is: Islamic year at Akbar’s crowning (963) + Current Gregorian (solar) year (2014) - Gregorian (solar) year at Akbar’s crowning (1556)
This gives us 1421, which, voila, is the current Bengali year today.
As Sen himself points out later on, it is fascinating to note that when, say, Durga Pujo dates will be calculated for the Bengali year 1421, the two events referenced (unknown to most Bengalis themselves) will be the migration of Prophet Mohammad from Mecca to Medina as well as Akbar’s coronation.