def calendar_date(jd_integer):
    """Convert Julian Day `jd_integer` into a Gregorian (year, month, day)."""
    k = jd_integer + 68569
    n = 4 * k // 146097
    k = k - (146097 * n + 3) // 4
    m = 4000 * (k + 1) // 1461001
    k = k - 1461 * m // 4 + 31
    month = 80 * k // 2447
    day = k - 2447 * month // 80
    k = month // 11
    month = month + 2 - 12 * k
    year = 100 * (n - 49) + m + k
    return year, month, day
