{
  "id": "days-until-earth-day",
  "version": "d140d9eac002",
  "status": "published",
  "name": "Days Until Earth Day",
  "question": "Days until Earth Day",
  "summary": "Counts the days from today, or any date you choose, to the next Earth Day, with its date and day of the week.",
  "category": "days",
  "subcategory": "countdowns",
  "url": "https://www.acalculator.org/days/days-until-earth-day",
  "markdown": "https://www.acalculator.org/days/days-until-earth-day.md",
  "kind": "function",
  "method": "Find the first date of Earth Day on or after the start date, then count the days from the start date to it.",
  "assumptions": [
    "Earth Day is April 22 every year.",
    "Start dates from January 1, 1970 to December 31, 2400 work, because the first Earth Day was on April 22, 1970.",
    "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."
  ],
  "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 Earth Day",
      "description": "Whole days from the start date to the next Earth Day; 0 on the day itself.",
      "format": "integer"
    },
    "date": {
      "label": "Date",
      "description": "The next date of Earth Day on or after the start date.",
      "format": "date-long"
    },
    "weekday": {
      "label": "Day of the week",
      "description": "The weekday of that date.",
      "format": "text"
    },
    "weeks": {
      "label": "In weeks",
      "description": "The same number of days in weeks and days.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "from": "2026-09-29"
    },
    "outputs": {
      "days": 205,
      "date": "2027-04-22",
      "weekday": "Thursday",
      "weeks": "29 weeks and 2 days"
    },
    "text": "From September 29, 2026, there are 205 days until Earth Day on Thursday, April 22, 2027."
  },
  "examples": [
    {
      "given": {
        "from": "2026-01-01"
      },
      "expect": {
        "date": "2026-04-22",
        "days": 111
      },
      "source": "the rule written again in Python 3 (datetime); docs/progress/WP-43.md"
    },
    {
      "given": {
        "from": "2026-04-23"
      },
      "expect": {
        "date": "2027-04-22",
        "days": 364
      },
      "source": "the rule written again in Python 3 (datetime); docs/progress/WP-43.md"
    }
  ],
  "sources": [
    "the rule written again in Python 3 (datetime); docs/progress/WP-43.md"
  ],
  "related": [
    "days-until-cinco-de-mayo",
    "days-until-mothers-day",
    "days-until-memorial-day",
    "days-until-summer",
    "days-until-fathers-day",
    "days-between-dates"
  ],
  "changelog": []
}