{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"add-days"},"result":{"entity_type":"calculator","id":"add-days","calculator_id":"add-days","canonical_url":"https://tttkmbb.com/everyday/add-days","name":"Add or Subtract Days Calculator","title":"Add Days to a Date Calculator – Date After N Days (or Before, with Negative N)","category":"everyday","category_name":"Everyday Life","tool_name":"calculate_date_plus_days","featured_mcp_tool":false,"description":"Adds a signed number of days to an ISO date and returns the resulting date and its weekday, using Gregorian calendar arithmetic in UTC.","use_when":"You need the date that is N days after (or before) a given date, e.g. a deadline 90 days from today or a return date 14 days after departure.","do_not_use_when":"You need the number of days between two known dates (use date-difference) or want to skip weekends when counting (not supported here).","inputs":[{"name":"start_date","label":"Start date","type":"date","required":false,"default":"today","description":"Date to start from (YYYY-MM-DD); defaults to the current UTC date.","example":"2026-09-23"},{"name":"days","label":"Days to add","type":"integer","unit":"days","required":true,"min":-1000000,"max":1000000,"description":"Number of days to add; negative values subtract.","example":90}],"outputs":[{"name":"result_date","label":"Result date","type":"date","decimals":4,"description":"start_date + days."},{"name":"weekday","label":"Weekday","type":"string","decimals":4,"description":"Day of the week of the result date."},{"name":"offset_text","label":"Offset","type":"string","decimals":4,"description":"The offset written as days and as weeks and days, before or after start_date."}],"input_schema":{"type":"object","properties":{"start_date":{"description":"Date to start from (YYYY-MM-DD); defaults to the current UTC date.","type":"string","format":"date","default":"today","examples":["2026-09-23"]},"days":{"description":"Number of days to add; negative values subtract. Unit: days.","type":"integer","minimum":-1000000,"maximum":1000000,"examples":[90],"x-unit":"days"}},"additionalProperties":false,"required":["days"]},"output_schema":{"type":"object","properties":{"result_date":{"description":"start_date + days.","type":"string","format":"date"},"weekday":{"description":"Day of the week of the result date.","type":"string"},"offset_text":{"description":"The offset written as days and as weeks and days, before or after start_date.","type":"string"}}},"formula":"result_date = start_date + days (calendar days, no weekend skipping); weekday = day of week of result_date","sources":[{"name":"Gregorian calendar – leap-year rule and month lengths (Wikipedia)","url":"https://en.wikipedia.org/wiki/Gregorian_calendar","type":"reference","retrieved_at":"2026-09-23"},{"name":"ISO 8601 – Date and time format (Wikipedia)","url":"https://en.wikipedia.org/wiki/ISO_8601","type":"reference","retrieved_at":"2026-09-23"}],"freshness":{"type":"daily","max_age_seconds":86400,"note":"Depends on the current date unless the date is supplied."},"examples":[{"name":"2026-09-23 + 90 days","inputs":{"start_date":"2026-09-23","days":90},"expected":{"result_date":"2026-12-22","weekday":"Tuesday","offset_text":"90 days (12 weeks 6 days) after 2026-09-23"},"url":"https://tttkmbb.com/api/v1/calculate/add-days?start_date=2026-09-23&days=90"},{"name":"2026-03-01 − 30 days","inputs":{"start_date":"2026-03-01","days":-30},"expected":{"result_date":"2026-01-30","weekday":"Friday","offset_text":"30 days (4 weeks 2 days) before 2026-03-01"},"url":"https://tttkmbb.com/api/v1/calculate/add-days?start_date=2026-03-01&days=-30"}],"faq":[{"q":"Are weekends or holidays skipped?","a":"No. Every calendar day counts. For business-day counting between two dates see date-difference."},{"q":"Is the start date day 0 or day 1?","a":"Day 0: adding 1 day to Monday gives Tuesday. For an inclusive convention (start date counts as day 1) add one day fewer."}],"tags":["add days to date","days from today","date plus days","subtract days","deadline date"],"related":[{"calculator_id":"date-difference","reason":"Inverse operation: days between two dates."},{"calculator_id":"days-until","reason":"Countdown from today to a target date."}],"links":{"html":"https://tttkmbb.com/everyday/add-days","markdown":"https://tttkmbb.com/everyday/add-days.md","json":"https://tttkmbb.com/everyday/add-days.json","api":"https://tttkmbb.com/api/v1/calculate/add-days","schema":"https://tttkmbb.com/api/v1/calculators/add-days","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-23"},"timestamp":"2026-09-23T23:29:04Z"}