Calculate date difference or add/subtract days
A date calculator finds the number of days, weeks, months, or years between two dates, or adds/subtracts a specific number of days from a starting date. It's used for deadlines, project planning, contract terms, and any calculation involving a span of calendar time.
Days Between = End Date − Start Date (accounting for calendar month lengths and leap years)
Enter both dates in difference mode; the calculator subtracts the start date from the end date, correctly accounting for varying month lengths and leap years, to give total elapsed days.
Use add/subtract mode with today as the starting date and 90 as the number of days to add — the calculator returns the resulting calendar date.
Yes — leap years (which add February 29) are automatically factored into any date span that includes them.
Calendar days count every day including weekends and holidays; business days exclude weekends (and sometimes public holidays), which is important for deadlines defined in 'business days.'
Conventions differ — some contexts count the start date as day zero (pure elapsed time), others count it as day one (inclusive counting) — check which convention applies to your specific deadline or requirement.