Date Calculator
Find the exact time between two dates — in years, months, days, weeks, and business days — or add and subtract a span to land on a new date.
From Wednesday, 1 January 2025 to Wednesday, 31 December 2025 is 364 days — 260 of them business days. Add 90 days to a start of 2025-01-01 and you land on Tuesday, 1 April 2025.
364 days
Full 2025 calendar year measured from the worked example
260 weekdays
Business days in that same span, excluding Saturdays and Sundays
UTC math
Daylight-saving and timezone shifts never change the day count
Turn a date range into an answer you can use
Durations, deadlines, and projected dates without manual calendar counting.
Calendar days vs business days
A 30-day window is rarely 30 working days. Separating weekdays from weekend days is what turns a date range into a realistic deadline, payroll period, or delivery estimate.
Add or subtract any span
Project a due date 90 days out, back-date a notice period, or find an anniversary. Month and year math clamps cleanly to valid calendar days, including leap years.
No timezone surprises
All arithmetic runs in UTC, so a span never gains or loses a day across daylight-saving boundaries — the same inputs always give the same answer.
How the Date Calculator Works
Formula
totalDays = (endDate − startDate) ÷ 86,400,000 ms
inclusive = totalDays + (include end day ? 1 : 0)
Years/Months/Days = calendar difference with day & month borrow
weeks = floor(totalDays ÷ 7); remainder = totalDays mod 7
weekdays = count of Monday–Friday across the span
weekends = span − weekdays
Add mode:
newDate = startDate shifted by ±amount in chosen unit
(month/year overflow clamps to the last valid day)Choose a mode
Measure the gap between two dates, or add/subtract a span from one date.
Enter your date(s)
Pick a start date, and an end date or an amount and unit.
Optionally include the end day
Switch between an exclusive gap and an inclusive count.
Read the breakdown
See total days, a years/months/days split, and business-day counts.
Use the result
Project deadlines, back-date notice periods, or confirm durations.
Business-day counts exclude weekends but not public holidays, which differ by country and region — subtract those separately if your deadline depends on them.
All date math runs in UTC using real calendar month lengths and leap years, so results are stable regardless of your local timezone or daylight-saving changes.
Frequently Asked Questions
Related Calculators
Pair this with adjacent date and time tools.