Date Calculator
Days between dates, add or subtract time, working days with custom holidays, and exact age — all in one place.
How to Use Date Calculator in 3 Steps
Pick what to calculate
Difference for the gap between two moments, Add / Subtract to move a date by years, months, weeks, days, hours or minutes, Working days to count or add business days around your own holiday list, and Age for an exact age on any date.
Enter the dates
Type or pick dates; results update as you type. Leave Start or Age on empty to use right now. Holidays accept one date per line in almost any format (ISO, 25 Dec 2026, 12/25/2026).
Copy or download
The result card shows the headline number plus breakdowns — total days, weeks, hours, ISO week, day of year and more. Copy everything as text or download as text or JSON.
Date Calculator — Frequently Asked Questions
How is “1 month” counted when adding?
Calendar-wise, the way people expect: 31 Jan + 1 month = 28 Feb (or 29 in a leap year), not 3 March. The day is clamped to the last day of the target month, and years follow the same rule for 29 Feb.
Why do years/months/days and total days differ?
The breakdown walks the calendar (whole years, then whole months, then the leftover days), so month lengths matter. Total days is the exact number of 24-hour days between the two moments. Both are correct — they answer different questions.
Which days count as working days?
Every day except the weekend pattern you choose in Settings and the dates in your holiday list. Weekends and holidays that overlap are counted once. “Working days to add” skips non-working days and lands on a working day; negative numbers go backwards.
Are daylight-saving changes handled?
Yes. Dates are interpreted in your device’s local time zone, so a 23- or 25-hour day on a DST switch shows up correctly in the hours total while the day count stays whole.
What does the ISO week mean?
ISO 8601 weeks start on Monday and week 1 is the week containing the year’s first Thursday — the numbering used across Europe and in most project tools. The tool also shows the day of the year (1–366).
Is my data uploaded anywhere?
No. Parsing and converting happen in JavaScript inside your browser tab. Your text and files are never sent to Toolity or anyone else.