Date Calculator
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Find days between dates (optionally business days) and add/subtract time. All calculations run locally in your browser.
1) Days Between Dates
2) Add / Subtract Time
About This Date Calculator
This privacy-first date calculator solves two everyday problems: count the number of days between two dates (with an option to include only business days), and add or subtract time from a base date in days, weeks, months, or years. Everything runs locally in your browser for speed and confidentiality—no uploads, no tracking.
For day counting, you can choose inclusive mode when both the start and end dates must be counted (e.g., an event spanning two listed days). Switch on business days to count only Monday through Friday; weekends are automatically excluded. Public holidays are not considered in this version—if you need holiday-aware results, subtract those dates manually from the total or adjust your base date accordingly.
When adding or subtracting time, the calculator supports days and weeks (with an optional “skip weekends” mode), as well as months and years. Month and year arithmetic is clamped to end-of-month to avoid invalid dates—for example, adding one month to 31 January yields the last valid day of February. Leap years are respected automatically when rolling dates forward or backward.
Under the hood, date math is performed at midnight UTC to reduce daylight-saving surprises across regions.
Results are shown in ISO format (YYYY-MM-DD) for clarity and easy copying into documents or
spreadsheets. This makes the tool well-suited for project plans, contracts, visa or waiting periods, rental
spans, and coursework scheduling—anywhere you need quick, reliable calendar arithmetic.
Tip: use the Set Today shortcut to prefill fields with today’s UTC date and accelerate common workflows.
Date Calculator: FAQs
What does Inclusive mean in day counting?
Inclusive counting includes both the start date and the end date in the total. Exclusive excludes one endpoint.
How are business days calculated?
Business days count Monday through Friday only and ignore public holidays. Weekend days are excluded.
Does the calculator handle months and leap years?
Yes. Month and year arithmetic is clamped to end-of-month, and leap years are respected when rolling dates.
Is my data private?
Yes. All calculations run locally in your browser. No data is uploaded or stored on a server.