Add years to a date
Add or subtract whole years and get the new date, so 15 March 2024 plus 2 years is 15 March 2026. A leap day lands on 28 February in common years, so 29 February 2024 plus 1 year gives 28 February 2025. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Date
- 2024-03-15
- Years
- 2
- Result
- 2026-03-15
- Year
- 2,026
- Month
- 3
- Day
- 15
Shifting a calendar date by a whole number of years is a common civil-date operation that still trips over leap days when the base day is the twenty-ninth of February. HR systems renew contracts on anniversary dates, warranty desks compute expiry years after a purchase, finance teams project fiscal milestones, and curriculum authors need a trusted oracle that rejects impossible bases such as the twenty-ninth of February in a common year. This tool accepts a strict ISO base date in year-month-day form plus an integer year offset that may be positive, negative, or zero, validates that the base day truly exists under Gregorian leap rules, advances or retreats the year, and when the base is February twenty-nine and the target year is not a leap year clamps the day to February twenty-eight so the result remains a real civil date.
How calendar year addition works without a clock
Start with a base calendar date written as year, month, and day in the international ISO form with hyphens and fixed widths so every client agrees on the same three integers.
Confirm that the year lies in a practical Gregorian range from year one through nine thousand nine hundred ninety-nine, that the month is between one and twelve, and that the day exists for that month under Gregorian leap rules: a year is a leap year when it is divisible by four, except that century years are leap years only when they are also divisible by four hundred.
That rule makes February twenty-nine legal in years such as two thousand twenty-four and two thousand, and illegal in two thousand twenty-three and nineteen hundred. When the triple is valid, add the integer year offset to the year component while keeping the month fixed. If the base day is February twenty-nine and the resulting year is not a leap year, clamp the day to twenty-eight so the output remains a real civil date; otherwise keep the original day of month.
Format the result as a four-two-two ISO string.
Where add-years calculators show up in real work
Human-resources platforms compute contract renewal and probation end dates as hire date plus one or two calendar years without pulling in a full scheduling library. Warranty and support desks set multi-year expiry dates from a purchase ISO string. Education and membership systems project anniversary windows for enrollment and dues.
Data engineers materialize derived columns for multi-year retention policies, multi-year licenses, and campaign end years from a single ISO base plus an integer offset stored in configuration. If you later need day offsets instead of year offsets, business-day counts that skip weekends, the difference in days between two dates, age from a birth date, or day-of-year ordinals alone, treat those as separate search intents and landings rather than overloading this add-years-to-a-date page.
What you can do with it
Contract and warranty anniversaries
Add one, two, or five calendar years to a hire or purchase ISO date to produce stable anniversary and expiry dates across hosts.
License and membership renewals
Project multi-year license end dates and membership renewals from a start ISO string plus a configured integer year offset.
Leap-day anniversary handling
Compute civil anniversaries for February 29 births or events with an explicit clamp to February 28 in non-leap result years.
FAQ
What does add years to a date mean?
It means taking a valid Gregorian calendar day and moving forward or backward by an integer number of calendar years, keeping the month and day when possible and clamping February 29 to February 28 when the result year is not a leap year.
How is February 29 handled?
If the base date is February 29 and the result year is a leap year, the result stays February 29.
What date format is required?
Strict ISO YYYY-MM-DD with four-digit year and two-digit month and day. Values like 2024-3-15 or 2024/03/15 are rejected so every client agrees on the same string.
What happens with an invalid base date such as 2023-02-29?
The error message explains that the day is not valid for that year and month.
What does it cost?
The browser tool is free and runs locally.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/date/add-years \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"date":"2024-03-15","years":2}'const res = await fetch("https://api.kit.forhosting.com/date/add-years", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"date": "2024-03-15",
"years": 2
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/date/add-years",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"date": "2024-03-15",
"years": 2
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/date/add-years", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"date":"2024-03-15","years":2}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"date":"2024-03-15","years":2}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/date/add-years", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"date": "2024-03-15",
"years": 2
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "date.add_years",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
What you send and what you get back
Send two required fields: date as a strict ISO calendar day such as two thousand twenty-four hyphen zero three hyphen one five, and years as a finite integer year count such as two, zero, or negative one. Classic checks include adding two years to the fifteenth of March two thousand twenty-four to reach the fifteenth of March two thousand twenty-six, adding one year to the twenty-ninth of February two thousand twenty-four to reach the twenty-eighth of February two thousand twenty-five with clamp true, adding four years to the same leap day to keep February twenty-nine in two thousand twenty-eight, and subtracting one year from a mid-year date to land on the prior anniversary. Missing fields, non-string dates, strings that do not match the four-two-two digit pattern, non-integer year offsets, and bases that match the pattern but are not real calendar dates all fail with invalid_input and are not charged. On success the response echoes the normalized base date, the integer years offset that was applied, the result ISO string after addition, the numeric year, month, and day of the result, a boolean is_leap_year flag for the result year, a boolean clamped_leap_day that is true only when February twenty-nine was reduced to February twenty-eight, and a short formula string that documents the leap clamp rule. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where add-years calculators show up in real work
Because this capability is a pure parse engine, API pricing is the published base of $0.002 per successful item and failed validation does not consume balance.