Bahman — month 11 of the Persian year

The month at a glance

Month number

11

In Iranian usage

Bahman

In Afghan usage

Dalw, or borj 11

Length

30 days

Gregorian window

January 20 to February 20

This month shares its Afghan name with a zodiac sign. What the tradition carries for the sign is on the sign's own page; this page is about the month.

Read about Aquarius, the sign

Bahman and Dalw: one month, two naming systems

Month 11 of the Solar Hijri calendar is called Bahman in Iranian usage and Dalw in Afghan usage. Both names belong to the same month of the same calendar. Neither is the real name and neither is a local variant of the other: the calendar has one set of months and two sets of names for them.

In Afghan usage the month names are the traditional borj names — Hamal, Sawr, Jawza, and onward to Hut — and a month is commonly referred to by its number instead. That is the convention behind a phrase like borj 11. It means the eleventh month of the year, which is this one: Dalw, the month Iranian usage calls Bahman.

Only the names differ. The month boundaries, the month lengths, and the leap rule are identical in both, so a date written in one system becomes the other by changing the name and nothing else.

Where the month sits in the year

Bahman, or Dalw, is month 11 of the Solar Hijri year, and it falls in winter. The month before it is Dey, called Jadi in Afghan usage. The month after it is Esfand, called Hut, which closes the year. When this month ends, one month of the year remains.

It runs 30 days, every year. That length comes from the calendar's own rule and does not vary: the leap day, in the years that have one, belongs to the final month of the year rather than to this one. So the length of Bahman is the same figure in a leap year as in any other.

Why its Gregorian window moves

The Solar Hijri year begins at the vernal equinox rather than on a fixed Gregorian day. The equinox arrives at a slightly different moment each year, and the Gregorian calendar keeps its own leap-year pattern, so the two slide against each other by a day and then correct. The lengths of the Persian months are set by the calendar's own rule, but the day the year starts on is determined by the equinox rather than chosen, and every later month inherits that shift.

The result is a narrow window rather than a single date. Across the 101 documented Persian years 1329 to 1429 — the Gregorian years 1951 to 2051 — this month began on 20 to 22 January and ended on 18 to 20 February. Over that whole span there are only 3 distinct start dates.

This is why a card printed with one fixed Gregorian range for Bahman is right in most years and quietly wrong in the rest. The dates gathered below spread across a few days for the same reason: the start is computed from the equinox, not assigned.

When Bahman began

The month lengths are set by the calendar's own rule, but the year starts at the spring equinox — so the Gregorian day this month begins on is not the same every year.

Across the 101 years below, Bahman began on 3 different Gregorian dates. A calendar printed with one fixed range is right for most of them and wrong for the rest.

From 1951-01-21 to 2051-02-19.

1. January 20

   20 yearsEnded February 18.

   1997, 2001, 2005, 2009, 2013, 2017, 2021, 2025, 2029, 2030, 2033, 2034, 2037, 2038, 2041, 2042, 2045, 2046, 2049, 2050

2. January 21

   78 yearsEnded February 19.

   1951, 1953, 1954, 1955, 1957, 1958, 1959, 1961, 1962, 1963, 1964, 1965, 1966, 1967, 1968, 1969, 1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2002, 2003, 2004, 2006, 2007, 2008, 2010, 2011, 2012, 2014, 2015, 2016, 2018, 2019, 2020, 2022, 2023, 2024, 2026, 2027, 2028, 2031, 2032, 2035, 2036, 2039, 2040, 2043, 2044, 2047, 2048, 2051

3. January 22

   3 yearsEnded February 20.

   1952, 1956, 1960

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