Why Is Durga Puja Celebrated in September or October?

Durga Puja is traditionally observed in September or October because its dates are determined by the Hindu lunisolar calendar, not by fixed dates in the Gregorian calendar. In Bengal and several other regions of South Asia, the principal Durga Puja rituals occur during Ashwin (Ashvina), the seventh month of the traditional Hindu calendar, generally corresponding to September–October in the Gregorian calendar.

The Role of the Hindu Calendar

The Hindu calendar combines lunar phases with the solar year. As a result, religious observances based on lunar months do not remain on the same Gregorian date every year.

Durga Puja is associated with the bright fortnight (Shukla Paksha) of Ashwin. In the Bengali tradition, the principal ritual sequence begins on Shashthi, the sixth lunar day of the bright fortnight, and concludes on Dashami, the tenth lunar day, also known as Vijaya Dashami.

Therefore, the Gregorian date changes from year to year even though the festival retains its position within the traditional calendar.

Why Ashwin Falls in September or October

Ashwin does not correspond exactly to one fixed Gregorian month. Its position moves within the Gregorian calendar because the two calendar systems measure time differently.

The lunar month is connected to the phases of the Moon, while the Gregorian calendar is a solar calendar containing fixed-length months. The traditional calendar periodically adjusts its relationship with the solar year. Consequently, the lunar dates associated with Durga Puja can fall at different points within September or October.

This is why Durga Puja may occur in late September in one year and in October in another. UNESCO describes Durga Puja in Kolkata as an annual festival celebrated in September or October.

Durga Puja and the Autumn Season

Durga Puja is also associated with Sharad, the autumn season of the traditional South Asian seasonal cycle. In Bengal, the festival forms part of the autumnal religious and cultural calendar.

The seasonal setting is significant to the identity of the festival, but the season itself does not determine the date. The precise dates are established through the relevant traditional calendar and astronomical calculations.

The connection between Durga Puja and autumn is therefore different from simply saying that the festival is an "autumn festival": its ritual timing is calendrical, while its seasonal setting is autumn.

What Is Mahalaya?

Mahalaya marks an important point in the annual Durga Puja cycle in Bengal. It is associated with the beginning of Devi Paksha, the fortnight dedicated to the Goddess, and is traditionally observed with rituals including tarpana, offerings made in remembrance of ancestors.

In popular Bengali observance, Mahalaya also marks the beginning of the period leading towards Durga Puja. The principal ritual worship of Durga, however, begins later, on Shashthi.

This distinction is useful for international readers because Mahalaya and the five principal Puja days are not the same thing.

Why Do the Main Puja Days Sometimes Cross Two Gregorian Months?

The principal sequence consists of:

• Maha Shashthi – the sixth lunar day

• Maha Saptami – the seventh lunar day

• Maha Ashtami – the eighth lunar day

• Maha Navami – the ninth lunar day

• Vijaya Dashami – the tenth lunar day

Because these are based on lunar tithis, their Gregorian dates can shift each year. In some years, the five principal days fall entirely within October; in others, part of the sequence may occur in late September and continue into October.

The dates are therefore not chosen simply as a fixed annual period such as "1–5 October." They are calculated according to the traditional calendar.

Why the Date Is Different Every Year

The annual variation can be seen in published calendar calculations. For example, Durga Puja dates listed for 2025 and 2026 differ substantially, while both remain within the Ashwin period and the September–October seasonal range.

This variation is a normal feature of a lunisolar calendrical system rather than a change in the festival's religious observance.

Is Durga Puja Always in September or October?

No. September and October describe the usual Gregorian-calendar range for the festival, particularly in Bengal and eastern India. Calendar calculations can place the observance at different points within this range.

Different regional traditions may also use distinct calendrical conventions and may observe related Durga or Navaratri festivals differently. Durga Puja as celebrated in Bengal should therefore be distinguished from the broader Sharad Navaratri traditions observed elsewhere in South Asia.

Why Is the Festival Celebrated at This Time?

The religious significance of Durga Puja is connected primarily with the worship of Goddess Durga and her victory over Mahishasura, the buffalo demon. The festival therefore has both a calendrical setting and a religious narrative.

In Bengal, Durga Puja is also associated with the autumnal worship of Durga and with the tradition known as Akal Bodhan, the invocation of the Goddess outside the conventionally expected period of her worship. The latter is connected in Hindu tradition with the story of Rama invoking Durga before his battle with Ravana.

These religious traditions help explain the festival's observance, while the Hindu calendar explains when its dates occur.

For international readers, the relationship between the traditional Hindu calendar and the Gregorian calendar is important for understanding the timing of Durga Puja.

The Hindu lunisolar calendar determines the traditional religious dates of the festival. Ashwin (Ashvina) identifies the lunar month associated with the principal observance, while Shukla Paksha, the bright or waxing fortnight, provides the period in which the main rituals occur.

Individual days are determined by tithis, the traditional lunar days. Shashthi, Saptami, Ashtami, Navami and Dashami therefore do not correspond to fixed Gregorian dates.

The Gregorian calendar is used internationally to express these dates in a familiar format. Depending on the year, the festival generally falls in September or October.

Durga Puja is also associated with Sharad, the autumn season in the traditional South Asian seasonal cycle. Thus, the festival's timing reflects both its traditional lunar calendar position and its seasonal association with autumn.

In Summary

Durga Puja is celebrated in September or October because its traditional observance follows the Hindu lunisolar calendar, particularly the Ashwin lunar month and its bright fortnight, rather than fixed Gregorian dates. The principal worship begins on Shashthi and culminates on Dashami. Since lunar tithis do not correspond to the same Gregorian dates every year, Durga Puja moves within the September–October period.

For a global audience, the simplest way to understand the timing is:

Durga Puja has a fixed place in the traditional Hindu calendar, but not a fixed date in the Gregorian calendar.