Date & Time
Date Calculator
Find the difference between two dates, or add and subtract days, weeks, months, years, and optional time from any start date.
Date difference
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Choose two dates to see the exact difference.
What is a date calculator?
A date calculator finds a future or past calendar date after adding or subtracting a chosen amount of time from a start date. It is helpful when you need a deadline, renewal date, follow-up date, expiry date, project milestone, notice period target, or a reminder without manually counting across month lengths and leap years.
Based on the pages currently ranking for this topic, users expect a simple start date, an add/subtract switch, inputs for years, months, weeks, and days, plus a clear result with the weekday. This page keeps those basics visible first, then adds advanced options for time, selected weekdays, repeat dates, and examples.
How to use this add/subtract date calculator
- Select the start date. Use today for questions like "what date is 30 days from now?"
- Choose Add for a future date or Subtract for a past date.
- Enter any combination of years, months, weeks, and days.
- Turn on Include time if the exact hour and minute matters.
- Turn on selected weekdays if only certain days should count, such as Monday to Friday.
- Use Repeat results when the same interval should be applied more than once.
How the calculation works
The calculator applies calendar units in a practical order: years, then months, then weeks and days, then optional hours and minutes. Months and years are not converted into a fixed number of days because real calendar months have different lengths.
If selected weekdays are enabled: weeks and days are counted only when the new date falls on an allowed weekday.
Month-end handling
When the target month has fewer days, the date is adjusted to the last valid day of that month. For example, January 31 plus 1 month becomes February 28 in a common year and February 29 in a leap year.
Examples
Example 1: 30 days from today
Set the start date to today, choose Add, enter 30 in Days, and calculate. The result gives the exact calendar date and weekday 30 days ahead.
Example 2: project deadline in 6 weeks
Choose the project start date, select Add, enter 6 in Weeks, and calculate. Use selected weekdays if your team counts only working days.
Example 3: date 90 days ago
Select today's date, choose Subtract, enter 90 in Days, and calculate. This is useful for audit periods, lookback windows, and eligibility checks.
Example 4: repeated monthly reminders
Enter 1 in Months and set Repeat results to 6. The calculator lists the next six monthly dates from your chosen start date.
When this calculator is useful
- Finding due dates for invoices, assignments, applications, and renewals.
- Planning reminders after 7, 14, 30, 60, or 90 days.
- Counting working-day style periods by selecting Monday to Friday only.
- Checking dates before or after contract periods, notice periods, subscriptions, and warranties.
- Building recurring milestone schedules with the repeat results option.
Frequently asked questions
What date is 30 days from today?
Click the "Today + 30 days" sample button or set the start date to today, choose Add, enter 30 days, and calculate.
How do I subtract days from a date?
Select the date you want to count back from, choose Subtract, enter the number of days, and calculate. The result will be the past date.
Does adding 1 month always add the same number of days?
No. A month is treated as a calendar unit. Adding 1 month from January 15 goes to February 15, while adding 1 month from January 31 goes to the last valid day in February.
Can I exclude weekends?
Yes. Turn on "Include only selected weekdays" and use the Mon-Fri preset. The calculator will count day-based movement only on weekdays.
Can I choose custom weekdays?
Yes. You can select any combination of weekdays. This helps for school timetables, rotating work patterns, or custom business schedules.
Can I include hours and minutes?
Yes. Turn on Include time, enter the start time, then add or subtract hours and minutes along with date units.
What is the repeat option for?
Repeat applies the same interval multiple times. For example, 1 month repeated 6 times lists six monthly dates.
Which calendar does this calculator use?
It uses the modern Gregorian calendar through your browser's local date handling. For legal, payroll, or tax deadlines, confirm the final date with the official rule that applies to your case.