How this instrument works
Plenty of everyday spans get measured in months rather than years or days: a 12-month lease, a 6-month probation period, an 18-month product roadmap. This instrument counts exactly that — feed it a start date and an end date and it works out how many whole calendar months separate them, plus the years those months roll up into and the days left over once the whole months are accounted for.
The month-count respects real calendar mechanics rather than treating every month as a fixed 30 days: a span from 15 January to 15 July is exactly 6 months regardless of how many actual days that covers, because February, April and August don't all run the same length. Underneath that breakdown, the instrument also reports the total days and total weeks spanned — an independently computed day-count that doesn't rely on the months arithmetic at all, which is how the two figures stay honest against each other.
Use it for anything measured in month-length terms: how far into a lease or loan you are, how many months a project has run, how many months old a piece of equipment or a subscription is. For a leaner tool that reports only the years-and-months figure without the day-level detail, this site's months-between-dates instrument runs the same underlying math with a narrower readout.
- Enter the start date — a lease's start, a project's kickoff, a subscription's first billing date.
- Enter the end date you want the count measured to.
- Read years, months and leftover days directly beneath the inputs.
- Check total days and total weeks for the same span further down.
Worked example — 15 Jan 2025 to 28 Jul 2026
Enter 2025-01-15 as the start date and 2026-07-28 as the end date. The instrument reports 1 year, 6 months and 13 days: one full year reaches 15 January 2026, six further full months reach 15 July 2026, and 13 leftover days reach 28 July 2026.
The independent day-count agrees at 559 total days, which comes to 79 total weeks. If the only figure that mattered were 'how many months into an 18-month lease,' the 1-year-6-month breakdown already gives that directly — 1 × 12 + 6 = 18 months.
Questions
Does a month here always mean 30 days?
No — it means a real calendar month, whatever length that particular month runs. Counting from 15 January to 15 February is one calendar month even though January has 31 days; the instrument tracks actual month boundaries rather than dividing the day-count by a fixed 30, which is why the months figure lines up with how contracts and leases actually define a month.
What's the difference between this and months-between-dates?
Same underlying math, different level of detail. This instrument reports the full breakdown — years, months, leftover days, plus total days and total weeks — for when you need the granular picture. Months-between-dates strips that down to just the years-and-months figure, useful when you only want a quick answer like '2 years, 4 months' without the extra totals.
Can I use this to count months for a loan or lease term?
Yes — enter the start date of the lease or loan and the date you want the count measured to, and the years-and-months figure tells you exactly how far into the term you are. Multiply the years by 12 and add the months for a single month-count number, like 18 months into a 24-month lease.
Why does the day count in the breakdown sometimes look small over a long span?
Because it's the remainder left over after the whole years and months are already subtracted out, not the total days in the span. A span of 1 year, 6 months and 13 days has consumed most of its length in the years-and-months part; the 13 days is only what's left after that — the totalDays figure further down is the actual full day count for the whole span.
Does it handle a start date near the end of a month, like the 31st?
Yes, using standard calendar-borrowing rules — if counting a whole month from the 31st would land on a date past the following month's end, like 31 January against a nonexistent 31 February, the arithmetic borrows correctly against the shorter month, the same convention this site's other calendar-span instruments use throughout.