{
  "id": "days-until-september",
  "version": "fa5c37a6ec80",
  "status": "published",
  "name": "Days Until September",
  "question": "Days until September",
  "summary": "Counts the days from today, or any date you choose, to September 1, the first day of the next September, with its weekday and the time in weeks and months.",
  "category": "days",
  "subcategory": "countdowns",
  "url": "https://www.acalculator.org/days/days-until-september",
  "markdown": "https://www.acalculator.org/days/days-until-september.md",
  "kind": "function",
  "method": "Find the first September 1 on or after the start date, then count the days from the start date to it.",
  "assumptions": [
    "The count is to September 1, the first day of the month. During September, it counts to September 1 of the next year.",
    "The start date itself is not counted: from the day before, the count is 1; on the day itself, it is 0.",
    "Dates are calendar days with no time of day, so a time zone or a daylight-saving change never adds or loses a day.",
    "Start dates from January 1, 1900 to December 31, 2400 work."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "from": {
        "title": "Count from",
        "description": "The date to count from. Today, unless you change it.",
        "type": "string",
        "format": "date"
      }
    }
  },
  "outputs": {
    "days": {
      "label": "Days until September",
      "description": "Whole days from the start date to the next September 1; 0 on September 1 itself.",
      "format": "integer"
    },
    "date": {
      "label": "Date",
      "description": "The next September 1 on or after the start date.",
      "format": "date-long"
    },
    "weekday": {
      "label": "Day of the week",
      "description": "The weekday of that September 1.",
      "format": "text"
    },
    "weeks": {
      "label": "In weeks",
      "description": "The same number of days in weeks and days.",
      "format": "text"
    },
    "months": {
      "label": "In months and days",
      "description": "The time to that date in whole months, then days.",
      "format": "duration"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "from": "2026-09-30"
    },
    "outputs": {
      "days": 336,
      "date": "2027-09-01",
      "weekday": "Wednesday",
      "weeks": "48 weeks",
      "months": {
        "years": 0,
        "months": 11,
        "days": 2
      }
    },
    "text": "From September 30, 2026, there are 336 days until September on Wednesday, September 1, 2027."
  },
  "examples": [
    {
      "given": {
        "from": "2026-09-28"
      },
      "expect": {
        "date": "2027-09-01",
        "days": 338,
        "weekday": "Wednesday"
      },
      "source": "U.S. Naval Observatory, Leap Years: the Gregorian leap year rule (https://aa.usno.navy.mil/faq/leap_years); Python 3 datetime: the next first of the month on or after the start date (docs/progress/WP-45/truth.py)"
    },
    {
      "given": {
        "from": "2026-09-01"
      },
      "expect": {
        "date": "2026-09-01",
        "days": 0,
        "weekday": "Tuesday"
      },
      "source": "U.S. Naval Observatory, Leap Years: the Gregorian leap year rule (https://aa.usno.navy.mil/faq/leap_years); Python 3 datetime: the next first of the month on or after the start date (docs/progress/WP-45/truth.py)"
    },
    {
      "given": {
        "from": "2026-09-02"
      },
      "expect": {
        "date": "2027-09-01",
        "days": 364,
        "weekday": "Wednesday"
      },
      "source": "U.S. Naval Observatory, Leap Years: the Gregorian leap year rule (https://aa.usno.navy.mil/faq/leap_years); Python 3 datetime: the next first of the month on or after the start date (docs/progress/WP-45/truth.py)"
    },
    {
      "given": {
        "from": "2028-02-29"
      },
      "expect": {
        "date": "2028-09-01",
        "days": 185,
        "weekday": "Friday"
      },
      "source": "U.S. Naval Observatory, Leap Years: the Gregorian leap year rule (https://aa.usno.navy.mil/faq/leap_years); Python 3 datetime: the next first of the month on or after the start date (docs/progress/WP-45/truth.py)"
    }
  ],
  "sources": [],
  "related": [
    "days-until-august",
    "days-until-october",
    "days-until",
    "days-between-dates"
  ],
  "changelog": []
}