Date difference
Plenty for project timelines, anniversaries, and contract expiry.
Counted by calendar months: Jan 31 to Mar 1 is 1 month 1 day, not 30 days. The day difference is shown alongside as a second measure for comparison.
When to use it
- You are working out a project schedule, probation period, lease end or leave request and need days, weeks and calendar months together, not a single figure.
- You need to check whether two dates are a full 30 days or a full 3 months apart — return windows, subscription cycles, contract milestones.
When not to
- You need hours or minutes between two times: this compares dates at midnight, so two times on the same day always differ by 0.
- You need working days with weekends and public holidays skipped: this counts calendar days only; use a business-day calendar for scheduling.
Both dates are processed in your browser; nothing is uploaded, written into the URL or stored locally — leave and medical dates are private too. Limits: calendar days only, so weekends and public holidays are not skipped; months advance by calendar month, and month-end dates can come out one month lower than expected; years are days ÷ 365 with no leap-year adjustment; time of day and time zones are ignored.
Frequently asked
Why can't I just divide the days by 30?
Months are 28–31 days long, so dividing by 30 is only an approximation. In a common year, 1 February to 1 March is 28 days but exactly one calendar month; 1 January to 1 February is 31 days and also one calendar month; dividing by 30 gives 0.93 and 1.03. A contractual “full month” normally means the corresponding date (15 January to 15 February), not 30 days. This tool advances by calendar month and shows the remainder in days; the year figure is a separate days ÷ 365 conversion, and the two cannot replace each other.
Should the count include both the start and end date?
By default no: it subtracts two midnights, so 1 January to 2 January is 1 day. Tick “include start and end” to add 1 and get 2 days. Leave, hospital stays and construction schedules often count both ends; hotel nights, leases and probation often count the start but not the end — one night is one day. Before you report 1 day or 2, agree on the convention and then decide whether to tick the box.
Calendar months and converted years disagree — which one should a contract use?
Whichever unit the clause names. “Three months” means the corresponding date in the calendar; “90 days” means calendar days, and between February and April the two can differ by 1–2 days. This tool shows days, calendar months and a 365-day year for comparison; the year figure is not a legal “full year”. Contracts, insurance and return windows follow the stated unit: if it says months, find the corresponding date; if it says days, count calendar days.