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Free online date calculator. Calculate days between dates or add/subtract days from a date.
7
days between
Date calculation is a fundamental task in software development. Common operations include finding the number of days between two dates, calculating project deadlines, determining age, scheduling recurring events, and computing time intervals for billing, analytics, and reporting.
Calendar day calculation counts each day on the calendar between two dates, regardless of whether it is a weekday, weekend, or holiday. A project spanning from Monday to the following Monday is 7 calendar days. Calendar day calculations are the standard for most software applications and legal contexts.
Business day calculation (also called working days) excludes weekends and optionally holidays. This is used for SLA tracking, court deadlines, shipping estimates, and project management. An order placed on Friday might ship in '3 business days' — arriving on Wednesday, not Monday, because Saturday and Sunday are excluded.
Date arithmetic also includes adding or subtracting units: days, weeks, months, and years. Adding months is more complex than adding days because months have variable lengths. Adding 1 month to January 31 could give February 28 (or 29 in leap years), depending on the implementation. JavaScript's Date object handles this by rolling over to the next month.
This calculator supports two modes: Date Difference (find days/weeks/months between two dates) and Add Days (add or subtract days from a starting date). All calculations run entirely in your browser. For production applications, consider timezone-aware libraries like date-fns or Day.js that handle edge cases like DST transitions correctly.
Calendar days count every day including weekends and holidays. Business days count only Monday through Friday (and optionally excluding holidays). A deadline of '5 calendar days' from Monday is Saturday; '5 business days' from Monday is the following Monday.
No. Adding 1 month to January 31 gives February 28 (or 29 in leap years). This is because months have different lengths. JavaScript and most programming languages handle this by capping the day to the last valid day of the target month. Always verify date arithmetic results for month-end dates.
This is typically caused by timezone issues. If you create dates without specifying a timezone, JavaScript uses midnight local time. When converted to UTC, this might shift the date by one day. Always be explicit about timezone handling when comparing or calculating dates.