Date Duration Calculator

Add or subtract time from any date to find a new date

Starting Date

Operation

Years

Months

Weeks

Days Enter at least one duration value

New Date —

Operation —

Starting Date —

Total Days —

Day of Week —

What Is a Date Duration Calculator?

A date duration calculator is a tool that adds or subtracts a specific duration (years, months, weeks, or days) from a given date to calculate a new date. This is essential for project planning, legal deadlines, financial calculations, and personal scheduling.

Common uses include:

Project management: Calculate project end dates from start dates and durations
Legal deadlines: Add required response periods to notice dates
Financial planning: Calculate loan maturity dates, payment due dates
Contract terms: Add contract duration to start date for end date
Warranty expiration: Add warranty period to purchase date
Subscription renewal: Calculate next billing date from start date

How to Add Days to a Date

Adding days to a date is the most common duration calculation:

Enter starting date: Select your beginning date
Select "Add Time": Choose the add operation
Enter number of days: Specify how many days to add
Click calculate: Get your new date instantly

Example: January 15, 2026 + 45 days = March 1, 2026

Business Applications of Date Duration

Project Management

Calculate end dates: Start date + project duration = deadline
Set milestones: Phase start + phase duration = phase end
Track deliverables: Kickoff + lead time = delivery date
Plan resources: Determine when resources are freed up

Financial Calculations

Loan maturity: Origination date + loan term = maturity date
Payment terms: Invoice date + Net 30 = due date
Bond maturity: Issue date + bond term = redemption date
CD maturity: Opening date + CD term = maturity date

Legal and Compliance

Response deadlines: Notice date + response period = deadline
Filing deadlines: Event date + statutory period = filing due date
Contract expiration: Start date + contract term = expiration
Statute of limitations: Incident date + limitation period = deadline

How to Subtract Time from a Date

Subtracting time is useful for working backwards from deadlines:

Common Use Cases

Reverse planning: Deadline - preparation time = start date
Order placement: Need-by date - lead time = order date
Travel planning: Departure - preparation days = packing start
Event planning: Event date - planning period = planning start

Example: Wedding on June 15 - 90 days = Start planning by March 17

Adding Months to Dates

Adding months is more complex than days because months have varying lengths:

How Month Addition Works

Same day of month: January 15 + 1 month = February 15
Month-end handling: January 31 + 1 month = February 28/29 (last day of Feb)
Year rollover: November 15 + 3 months = February 15 (next year)

Common Applications:

Quarterly reviews (add 3 months)
Monthly subscriptions (add 1, 6, or 12 months)
Pregnancy due dates (add 9 months)
Lease terms (add 6, 12, 24 months)

Adding Years to Dates

Adding years accounts for leap years automatically:

Leap Year Handling

Regular dates: January 15, 2024 + 1 year = January 15, 2025
Leap day: February 29, 2024 + 1 year = February 28, 2025
Multiple years: Handles all intervening leap years

Common Applications:

Contract renewals (1-5 year terms)
Warranty expiration (1-3 year warranties)
License expiration (annual licenses)
Anniversary calculations

Combining Multiple Time Units

You can add multiple time units simultaneously:

Example: Calculate a complex duration:

Start: January 1, 2026
Add: 1 year, 3 months, 2 weeks, 5 days
Result: April 20, 2027

This is useful for:

Complex project timelines
Multi-phase contracts
Staggered payment schedules
Compound warranty periods

Practical Examples

90-Day Notice Period

Scenario: You're resigning and need to provide 90 days notice

Today's date: February 15, 2026
Add 90 days
Last working day: May 16, 2026

Net 30 Payment Terms

Scenario: Invoice issued, payment due in 30 days

Invoice date: March 5, 2026
Add 30 days
Payment due: April 4, 2026

6-Month Project Timeline

Scenario: Project starts today, duration is 6 months

Project start: January 10, 2026
Add 6 months
Expected completion: July 10, 2026

People Also Search For

Add days to a date calculator?

To add days to a date, enter a start date and the number of days to add; the calculator returns the resulting date instantly. For example, enter today's date in the Starting Date field, select "Add Time," type 30 in the Days field, and click Calculate — you'll see exactly what date falls 30 days from now, including the day of the week.

What date is 30 days from today?

Enter today's date as the start date, select "Add Time," and type 30 in the Days field to find the date exactly 30 days from now. This works for any number of days, weeks, months, or years — just change the value in the corresponding field. The calculator returns the resulting date along with the full weekday name so you know exactly when it lands.

Date calculator add months?

Adding months is trickier than adding days because months have different lengths, but this calculator handles all the edge cases automatically. February, leap years, and month-end situations (like January 31 + 1 month becoming February 28 or 29) are all resolved correctly. Simply enter your start date, select "Add Time," type the number of months, and calculate.

Subtract days from a date?

Use the Subtract Time mode to remove days from a date — useful for answering questions like "what date was 90 days ago?" or "when should I have started a 45-day project that's due today?" Select "Subtract Time" from the Operation dropdown, enter the number of days (or weeks, months, years), and the calculator returns the earlier date. Ideal for working backwards from deadlines and planning reverse timelines.

What day will it be in X days?

Enter today's date as the start date, set the desired number of days in the Days field, and the result includes the full weekday name of the future date. So if you want to know what day it will be in 45 days, the calculator shows you both the calendar date and whether it falls on a Monday, Wednesday, or any other day — helpful for scheduling meetings, appointments, or deadlines.

How to calculate a date 6 months from now?

Adding 6 calendar months is not the same as adding 180 days — months vary in length, so our calculator adds exactly 6 calendar months and accounts for varying month lengths automatically. For example, August 31 plus 6 months becomes February 28 (or 29 in a leap year), not March 2. Enter today's date, select "Add Time," type 6 in the Months field, and click Calculate to get the precise date 6 months from now.

Frequently Asked Questions

How do I add days to a date?

Enter your starting date, select "Add Time," enter the number of days in the "Days" field, and click "Calculate New Date." The result will show your new date.

How do I subtract days from a date?

Enter your starting date, select "Subtract Time," enter the number of days, and click calculate. The calculator will show the earlier date.

What date is 90 days from today?

Use the calculator with today's date as the starting date, select "Add Time," enter 90 in the days field, and calculate. This is useful for 90-day notice periods.

How do I calculate a date 6 months from now?

Enter today's date, select "Add Time," enter 6 in the months field, and calculate. The result accounts for varying month lengths automatically.

Does this calculator account for leap years?

Yes! The calculator automatically handles leap years when adding or subtracting time. Leap year dates (like February 29) are properly accounted for.

Can I combine years, months, weeks, and days?

Absolutely! You can enter values in multiple fields (e.g., 1 year, 3 months, 2 weeks, 5 days) and the calculator will add them all together for the final result.

What happens when adding months to the 31st?

If the starting date is the 31st and the target month has fewer days (like February with 28/29), the calculator returns the last day of that month.

How do I calculate "Net 30" payment due dates?

Enter the invoice date, select "Add Time," enter 30 days, and calculate. The result is your payment due date under Net 30 terms.

Can I use this for working backwards from a deadline?

Yes! Enter your deadline date, select "Subtract Time," enter the preparation time needed, and calculate to find when you should start.

What date is 3 weeks from today?

Enter today's date, select "Add Time," enter 3 in the weeks field (or 21 in the days field), and calculate to see the date 3 weeks from now.

Does this handle daylight saving time?

The calculator works with dates only (not specific times), so daylight saving time doesn't affect the results. It calculates calendar dates accurately regardless of DST.

Can I calculate contract end dates?

Yes! Enter the contract start date, select "Add Time," enter the contract duration (in years, months, or days), and calculate to find the end date.

How accurate is this date calculator?

This calculator is 100% accurate. It properly accounts for varying month lengths (28-31 days), leap years, and year boundaries when adding or subtracting time.

Can I calculate warranty expiration dates?

Absolutely! Enter the purchase date, select "Add Time," enter the warranty period (e.g., 1 year, 2 years, 90 days), and calculate to find when the warranty expires.

What's the difference between adding weeks and days?

Adding weeks is simply a convenience - 1 week = 7 days. You can use either field, and the result will be the same. For example, adding 2 weeks is the same as adding 14 days.