Month counter
From January 2020 to June 2024 there are 53 whole months. Enter just the year and month of each date, with no day needed, and get the month count for a lease, a job tenure, a subscription or a project window. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Start year
- 2,020
- Start month
- 1
- End year
- 2,024
- End month
- 6
- Months
- 53
- Month count
- 53
A month counter answers a narrower question than a full date-difference tool: given only the year and month of two calendar dates, how many whole months sit between them? People look up that number when they price a lease, count job tenure, schedule a subscription, or convert a project window into billing periods.
What a whole-month count between two year-month dates means
A calendar month is a named slot in the civil year — January through December — not a fixed number of days. When someone asks how many months lie between two dates and they only know the year and the month of each, they are not asking for remaining days, leap-day adjustments, or an age in years-months-days. They want the integer gap on the year-month grid.
That gap is the difference of two ordinal month indexes: twelve times the year plus the month number. Subtract the start index from the end index and you have the signed whole-month count. January 2020 to January 2021 is twelve months; January 2020 to February 2020 is one month; the same year and month is zero.
Reverse the pair and the signed result flips sign while the absolute month count stays the same. This is the same arithmetic payroll systems use for completed billing periods and the same identity a lease clause means when it says “a term of twenty-four months from March 2024.” Because the day of month is never supplied, the result does not depend on whether a month has twenty-eight or thirty-one days, and it does not clamp end-of-month dates the way a day-aware adder must.
That is a feature of the search intent, not a missing day field: a month counter is the tool you open when the day is irrelevant or unknown.
Where a month counter earns its keep
Housing and facilities teams count months between a move-in year-month and a move-out year-month when a lease is written in calendar months rather than exact days. Human-resources tools report tenure as completed months from a hire year-month to a review year-month without inventing a missing day of month. Subscription and SaaS billing desks convert a plan window into a month count before they apply a monthly rate.
Project managers turn a kickoff month and a ship month into a duration they can drop into a Gantt or a fixed-price quote. Failed validation does not consume balance.
What you can do with it
Lease and rental terms
Count whole months from a move-in year-month to a move-out year-month when the contract is written in calendar months, not exact days.
Employment tenure in months
Report completed months from a hire year-month to a review or exit year-month without inventing a missing day of month.
Subscription and project windows
Turn a plan start month and an end month into a billing-period count, or a kickoff month and a ship month into a project duration.
FAQ
What happens if a month or year is invalid?
Months must be integers from 1 to 12 and years must be integers from 1 to 9999. Those failures are not billed.
Does the month counter need a day of month?
No. The search intent is the year-month grid only. For day-aware spans with remaining days, use a date-difference tool that accepts full calendar dates.
What if the end date is before the start date?
The same pair in reverse order flips the sign of months only.
Is the start month counted as one of the months?
No, the counter measures the gap between the two months. January 2020 to February 2020 is one month, January 2020 to January 2021 is twelve, and the same year and month gives zero.
What can I use a month counter for?
For anything written in calendar months rather than days: a lease from move-in to move-out, completed months of employment for a review, a subscription window turned into billing periods, or a project from kickoff to delivery for a quote.
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/life/month-counter \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"start_year":2020,"start_month":1,"end_year":2024,"end_month":6}'const res = await fetch("https://api.kit.forhosting.com/life/month-counter", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"start_year": 2020,
"start_month": 1,
"end_year": 2024,
"end_month": 6
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/life/month-counter",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"start_year": 2020,
"start_month": 1,
"end_year": 2024,
"end_month": 6
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/life/month-counter", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"start_year":2020,"start_month":1,"end_year":2024,"end_month":6}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"start_year":2020,"start_month":1,"end_year":2024,"end_month":6}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/life/month-counter", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"start_year": 2020,
"start_month": 1,
"end_year": 2024,
"end_month": 6
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "life.month_counter",
"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.
Limits
year_min | 1 |
year_max | 9999 |
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
This capability accepts start_year, start_month, end_year, and end_month, validates each year as an integer from 1 to 9999 and each month as an integer from 1 to 12, then applies the identity months equals end year minus start year, times twelve, plus end month minus start month. The signed difference is months; the absolute value is month_count. An invalid month or year fails with invalid_input and is not billed.
Input contract, validation, and the response you get back
Years must fall between 1 and 9999 inclusive. Months must fall between 1 and 12 inclusive. Numeric strings such as "2020" or "06" are accepted; booleans, objects, empty strings, and non-integers are not. The engine never reads the system clock, so two callers who send the same four integers always receive the same object. Send four required whole integers: start_year and start_month for the earlier or later bound you treat as the start, and end_year and end_month for the other bound. Aliases from_year, begin_year, from_month, begin_month, to_year, until_year, to_month, and until_month map onto the same four fields so a form or a script can use the names that already exist in its schema. If either date has an invalid month or year, the task fails with invalid_input that names the field — those failures are not billed. On success the body echoes the four validated integers, returns months as the signed difference, returns month_count as the absolute month count, and restates the formula so a client can print the identity next to the answer. Example: start_year 2020, start_month 1, end_year 2024, end_month 6 yields months 53 and month_count 53, because four years are forty-eight months and January to June adds five more.
Where a month counter earns its keep
Keep both year-month pairs in the request, pin month_count in tests, and you get a reproducible month count for leases, tenure, and billing without standing up a calendar library of your own.
Technical questions
How does the month counter compute whole months between two dates?
It takes start_year, start_month, end_year, and end_month and returns months = (end_year − start_year) × 12 + (end_month − start_month). month_count is the absolute value of that signed difference.
What does the month counter cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.