Add or subtract calendar days, weeks, months, or years from any specific date to find a future or past date precisely.
Monday
December 7th, 2026
Starting from Nov 7th, 2026, we added exactly 30 d. This perfectly accounts for leap years and irregular month lengths automatically.
Choose a start date, select add or subtract, and enter the interval. You can combine years, months, weeks, and days. These are calendar intervals, not business days; use the separate duration calculator when you already have both dates.
Try this toolCount calendar days, weeks, months, and years between two dates. Choose whether to include the end date and compare the date-duration breakdown.
Calculate age from a date of birth to today or a chosen date. See years, months, days, total days, and the next birthday countdown.
Find the duration between clock times or add and subtract hours and minutes. Compare start and end times, including a modeled crossing of midnight.
Adding days together sounds simple, until you introduce the chaos of the Gregorian calendar. Months have irregular days (28, 29, 30, 31). Leap years occur every 4 years (mostly). Our Date Calculator isolates you from calendar arithmetic, providing perfect timeline projections.
If you add precisely one month to January 31st, what day does it land on? February doesn't have 31 days. Does it roll into March, or snap to February 28th / 29th? Standards state that it maps to the end of the target month. Our calculator natively handles month-end ceiling operations automatically.
If you need to calculate the inverse—finding exactly how many days passed between two calendar dates—you need the Date Duration tool.