Date & Time
Age, duration & timezone calculators
Date Add/Subtract Calculator
Add or subtract days, weeks, months, years or business days from a date and get the resulting date and weekday. Month/year math clamps to valid dates (Jan 31 + 1 month = Feb 28, never Mar 3); business days skip weekends and US federal holidays. DST-safe UTC math, computed entirely in your browser. Accurate, instant and free — for United States.
What these mean:
What these mean:
Adding 30 days to 2026-06-24 gives 2026-07-24 (Friday).
Result date
2026-07-24
Weekday
Friday
Days from start
+30 days
Adding 30 days to 2026-06-24 lands on 2026-07-24 (Friday).
Month/year math clamps to valid dates
How we calculate
How we calculate this
Reviewed by Reckonist Editorial · Last reviewed July 2026. Figures follow the methods and sources set out in our editorial standards.
Dates are computed on UTC (DST-safe); month/year math clamps to valid dates; business days use the US federal-holiday calendar.
ISO-8601 · US federal holidays
Take it further: count the gap between two dates with the Date Difference Calculator, or find the ISO week with the Week Number Calculator.
Add or subtract days and weeks
The simplest case shifts a date by a whole number of days or weeks. A week is just seven calendar days, so adding two weeks is adding 14 days. The tool returns the resulting date, its weekday, and the signed number of days from the start — plus month, year and business-day modes.
Days & weeks
calendar days on UTC
result = start + n × 86,400,000 ms · weeks → n × 7 days
Computed on UTC midnights so a day is always a full calendar day (DST-safe).
Direction
add or subtract
subtract → n is negated (step backward)
Subtracting moves the date earlier; business-day mode steps backward over weekends and holidays too.
- 1Add the days: 24 Jun 2026 + 30 days = 2026-07-24.
- 2Read the weekday: 2026-07-24 is a Friday.
Months — with the end-of-month clamp
Adding a month shifts the month field and clamps to a valid day when the target month is shorter. 31 January 2026 plus 1 month is 28 February 2026 — the last day of February — not 3 March. This month-end clamp is the exact bug naive adders get wrong, so the tool applies it explicitly.
Worked example · 31 Jan + 1 month
Years — the 29 February clamp
Adding a year shifts the year field and clamps a leap day when the target year is not a leap year. 29 February 2028 plus 1 year is 28 February 2029, because 2029 has no 29 February; adding four years lands back on 29 February 2032.
Why the clamp is correct
Business / working days — weekends and observed holidays
Business (working) days are the weekdays — Monday to Friday — skipping weekends and public holidays. The tool steps one day at a time, skipping Saturdays, Sundays and US federal holidays on their observed dates, until it has counted the requested number of working days. Subtracting business days steps backward the same way.
Worked example · +10 business days from 24 June 2026
What date is N days from today?
Set the start date to today and add the number of days to answer “30 days from today”, “90 days from today” or “45 business days from today” in one step. The result shows the date and its weekday, and everything is computed in your browser, so the answer is stable regardless of your time zone.
Everything runs in your browser
Frequently asked questions
Add the number of days to the start date. 24 June 2026 plus 30 days is 24 July 2026, which is a Friday. This calculator shifts a date forward or back by days, weeks, months, years or business days and shows the resulting date, its weekday and the signed day distance from the start.
Adding a month clamps to the end of the target month rather than overflowing into the next one. 31 January 2026 plus 1 month is 28 February 2026 (or 29 February in a leap year), not 3 March. This month-end clamp is the single most common bug in naive date adders, so the tool applies it explicitly.
A leap day rolls back to 28 February in a non-leap year. 29 February 2028 plus 1 year is 28 February 2029, because 2029 has no 29 February. Adding four years lands back on 29 February 2032, the next leap year.
Business (working) days are the weekdays — Monday to Friday — skipping weekends and public holidays. The tool steps one day at a time, skipping Saturdays, Sundays and US federal holidays (using observed dates), until it has counted the requested number of working days. Subtracting business days steps backward the same way, which answers “N working days before a deadline”.
Yes. Business-day math skips US federal holidays on their observed dates — a holiday that lands on a Saturday is observed on the preceding Friday, and one on a Sunday on the following Monday. For example, 4 July 2026 falls on a Saturday and is observed on Friday 3 July, so a business-day span crossing that week skips 3 July.
No. All calculations run on UTC midnights, so adding a day is always a full calendar day even across a daylight-saving transition where a local day is 23 or 25 hours long. Doing the math in local time across a DST boundary is a classic source of off-by-one errors; anchoring to UTC avoids it.
Set the start date to today and add the number of days. The calculator returns the resulting date and its weekday, so “90 days from today” or “45 business days from today” is a single step. Because the math is client-side and DST-safe, the answer is stable regardless of your time zone.
Method & references
Methodology: days/weeks add n (× 7 for weeks) calendar days on UTC midnights; months and years shift the calendar field and clamp overflow to the last valid day (Jan 31 + 1mo → Feb 28/29; Feb 29 + 1yr → Feb 28); business days step ±1 day skipping weekends and US federal holidays with observed-date rules (Sat → Fri, Sun → Mon). All calculations run client-side and nothing is stored.
Cross-links
How we calculate this
Reviewed by Reckonist Editorial · Last reviewed July 2026. Figures follow the methods and sources set out in our editorial standards.
Dates are computed on UTC (DST-safe); month/year math clamps to valid dates; business days use the US federal-holiday calendar with observed-date rules. Reference: ISO-8601.
Keep going
Same-category tools follow this colour; a cross-category link keeps its own.