{
  "id": "how-old-am-i-born-in-1971",
  "version": "df8f7ae37848",
  "status": "published",
  "name": "How Old Am I If I Was Born in 1971",
  "question": "How old am I if I was born in 1971?",
  "summary": "Works out the age today, or on any date, of someone born in 1971: one number after their birthday, one less before it.",
  "category": "days",
  "subcategory": "age",
  "url": "https://www.acalculator.org/days/how-old-am-i-born-in-1971",
  "markdown": "https://www.acalculator.org/days/how-old-am-i-born-in-1971.md",
  "kind": "function",
  "method": "Age = year of the date − birth year, once the birthday in that year has come; one less before it.",
  "assumptions": [
    "Age counts completed years, as in everyday use: you turn 1 on your first birthday.",
    "Without the month and day of birth, the age on most dates is one of two numbers; on the date’s year the birthday decides which.",
    "Only the year is known, so in the birth year itself the age shows as 0 even on a date before the birth.",
    "Someone born on February 29 has a birthday on February 28 or March 1 in other years; either way, the year difference is the same."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "year": {
        "title": "Year you were born",
        "description": "The year of birth, 1900 to 2100.",
        "type": "string",
        "enum": [
          "2100",
          "2099",
          "2098",
          "2097",
          "2096",
          "2095",
          "2094",
          "2093",
          "2092",
          "2091",
          "2090",
          "2089",
          "2088",
          "2087",
          "2086",
          "2085",
          "2084",
          "2083",
          "2082",
          "2081",
          "2080",
          "2079",
          "2078",
          "2077",
          "2076",
          "2075",
          "2074",
          "2073",
          "2072",
          "2071",
          "2070",
          "2069",
          "2068",
          "2067",
          "2066",
          "2065",
          "2064",
          "2063",
          "2062",
          "2061",
          "2060",
          "2059",
          "2058",
          "2057",
          "2056",
          "2055",
          "2054",
          "2053",
          "2052",
          "2051",
          "2050",
          "2049",
          "2048",
          "2047",
          "2046",
          "2045",
          "2044",
          "2043",
          "2042",
          "2041",
          "2040",
          "2039",
          "2038",
          "2037",
          "2036",
          "2035",
          "2034",
          "2033",
          "2032",
          "2031",
          "2030",
          "2029",
          "2028",
          "2027",
          "2026",
          "2025",
          "2024",
          "2023",
          "2022",
          "2021",
          "2020",
          "2019",
          "2018",
          "2017",
          "2016",
          "2015",
          "2014",
          "2013",
          "2012",
          "2011",
          "2010",
          "2009",
          "2008",
          "2007",
          "2006",
          "2005",
          "2004",
          "2003",
          "2002",
          "2001",
          "2000",
          "1999",
          "1998",
          "1997",
          "1996",
          "1995",
          "1994",
          "1993",
          "1992",
          "1991",
          "1990",
          "1989",
          "1988",
          "1987",
          "1986",
          "1985",
          "1984",
          "1983",
          "1982",
          "1981",
          "1980",
          "1979",
          "1978",
          "1977",
          "1976",
          "1975",
          "1974",
          "1973",
          "1972",
          "1971",
          "1970",
          "1969",
          "1968",
          "1967",
          "1966",
          "1965",
          "1964",
          "1963",
          "1962",
          "1961",
          "1960",
          "1959",
          "1958",
          "1957",
          "1956",
          "1955",
          "1954",
          "1953",
          "1952",
          "1951",
          "1950",
          "1949",
          "1948",
          "1947",
          "1946",
          "1945",
          "1944",
          "1943",
          "1942",
          "1941",
          "1940",
          "1939",
          "1938",
          "1937",
          "1936",
          "1935",
          "1934",
          "1933",
          "1932",
          "1931",
          "1930",
          "1929",
          "1928",
          "1927",
          "1926",
          "1925",
          "1924",
          "1923",
          "1922",
          "1921",
          "1920",
          "1919",
          "1918",
          "1917",
          "1916",
          "1915",
          "1914",
          "1913",
          "1912",
          "1911",
          "1910",
          "1909",
          "1908",
          "1907",
          "1906",
          "1905",
          "1904",
          "1903",
          "1902",
          "1901",
          "1900"
        ]
      },
      "on": {
        "title": "Age on",
        "description": "The date to find the age on. Today, unless you change it.",
        "type": "string",
        "format": "date"
      }
    }
  },
  "outputs": {
    "ages": {
      "label": "Age in years",
      "description": "The age on the date: two numbers, the lower one before that year’s birthday.",
      "format": "text"
    },
    "after": {
      "label": "From the birthday on",
      "description": "The age on the date if the birthday in that year has come.",
      "format": "integer"
    },
    "before": {
      "label": "Before the birthday",
      "description": "The age on the date if the birthday in that year is still to come.",
      "format": "integer"
    },
    "detail": {
      "label": "Which one",
      "description": "Which age applies when.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "year": "1971",
      "on": "2026-09-29"
    },
    "outputs": {
      "ages": "54 or 55",
      "after": 55,
      "before": 54,
      "detail": "55 if the birthday in 2026 has come, 54 if not"
    },
    "text": "Born in 1971, on September 29, 2026 the age is 54 or 55: 55 if the birthday in 2026 has come, 54 if not."
  },
  "examples": [
    {
      "given": {
        "year": "1971",
        "on": "2026-09-28"
      },
      "expect": {
        "after": 55,
        "before": 54,
        "ages": "54 or 55"
      },
      "source": "hand calculation: 2026 − 1971 = 55 after the 2026 birthday, one less before it"
    },
    {
      "given": {
        "year": "1971",
        "on": "2030-01-01"
      },
      "expect": {
        "after": 59,
        "before": 58
      },
      "source": "hand calculation: 2030 − 1971 = 59; on January 1 only a January 1 birthday has come"
    },
    {
      "given": {
        "year": "1971",
        "on": "1971-12-31"
      },
      "expect": {
        "after": 0,
        "ages": "0"
      },
      "source": "hand calculation: 1971 − 1971 = 0"
    }
  ],
  "sources": [],
  "related": [
    "how-old-am-i",
    "how-old-am-i-born-in-1970",
    "how-old-am-i-born-in-1972",
    "dob",
    "chronological-age"
  ],
  "changelog": []
}