Question 1

How do I calculate the number of days between two dates?

Accepted Answer

Select 'Date Difference' mode, choose your start and end dates using the date picker. The calculator instantly shows the result in years, months, days, as well as total weeks, days, hours, and minutes. Toggle 'Include End Date' to count both the start and end dates in your calculation. Our calculator handles all calendar complexities including leap years automatically.

Question 2

Can I calculate business days only?

Accepted Answer

Yes! Disable the 'Include All Days' option to reveal weekday selection. Choose which days to include (Monday-Sunday) to calculate only business days, weekends, or any custom weekday combination. This is perfect for project planning when you need to exclude weekends or specific non-working days. The calculator shows both total days and your selected days count.

Question 3

How do I add days, months, or years to a date?

Accepted Answer

Select 'Add Time' mode, choose your starting date, then enter the number of years, months, and days to add. The calculator instantly shows the resulting date with day of week. The calculator handles month-end dates intelligently - adding 1 month to January 31st gives February 28th (or 29th in leap years) since February doesn't have 31 days.

Question 4

What is the difference between inclusive and exclusive date counting?

Accepted Answer

Exclusive counting (default) counts from the start date up to (but not including) the end date. For example, January 1 to January 5 = 4 days. Inclusive counting includes both the start and end dates, so January 1 to January 5 = 5 days. Toggle 'Include End Date' to switch between modes. Most date calculations use exclusive counting, but inclusive is common for rental periods or event durations.

Question 5

Does the calculator handle leap years correctly?

Accepted Answer

Yes, the calculator automatically handles leap years using the correct algorithm: years divisible by 4 are leap years (366 days), except years divisible by 100 are not leap years, unless they're also divisible by 400. For example, 2000 was a leap year (divisible by 400), but 1900 was not (divisible by 100 but not 400). This ensures accurate calculations across any date range.

Question 6

How do I calculate someone's exact age?

Accepted Answer

Use 'Date Difference' mode. Set the start date to their birth date and the end date to today (or any future date). The result shows their age in years, months, and days. For example, born January 15, 1990 to November 20, 2024 shows 34 years, 10 months, 5 days. The calculator also displays total days lived, which includes leap years.

Question 7

Can I calculate project deadlines and milestones?

Accepted Answer

Absolutely! Use 'Add Time' mode to calculate deadlines. Start with your project start date, add the duration (e.g., 3 months, 15 days), and get the deadline date. For business day calculations, disable 'Include All Days' and select only working days (Monday-Friday). This gives you accurate working day counts for resource planning and scheduling.

Question 8

What happens when I add months to a date at month-end?

Accepted Answer

The calculator uses smart month-end handling. When adding months to dates like January 31st results in a month with fewer days (like February with 28/29 days), it adjusts to the last valid day of that month. For example: January 31 + 1 month = February 28 (or 29 in leap years). Similarly, August 31 + 1 month = September 30, since September has only 30 days.

Question 9

How do I subtract time from a date?

Accepted Answer

Select 'Subtract Time' mode, choose your starting date, then enter the years, months, and days to go back in time. This is useful for calculating retroactive dates, historical references, or backdating documents. For example, subtracting 1 year, 6 months from November 20, 2024 gives May 20, 2023. The calculator handles all calendar complexities including leap years.

Question 10

Can I use this calculator for legal or contract dates?

Accepted Answer

Yes, the date calculator is accurate for legal and contract calculations. For contract terms, use 'Add Time' mode from the start date. For statute of limitations or deadline compliance, use 'Date Difference' to count days remaining. Enable business day calculations when contracts specify 'business days' or 'working days'. However, always verify critical legal dates with appropriate professionals as laws vary by jurisdiction.

Question 11

What are ISO week numbers and how are they calculated?

Accepted Answer

ISO 8601 week numbering is an international standard where week 1 is the first week containing at least 4 days in January (or containing January 4th). All weeks start on Monday and end on Sunday. A year has 52 or 53 weeks. This system is used globally for business planning, manufacturing, and logistics. Our calculator handles ISO week numbering automatically in date calculations.

Question 12

Is my date information private and secure?

Accepted Answer

Absolutely! All date calculations happen entirely in your browser using JavaScript. Your dates, calculations, and results never leave your device. There's no server transmission, database storage, or tracking. The calculator works offline after initial page load and stores nothing. This makes it perfect for confidential date calculations like legal deadlines, personal planning, or sensitive project dates.

Date CalculatorCompute & Compare

Calculation Mode

Date Difference

Add Time

Subtract Time

Select Dates

Calculation Options

Calculate Dates with Precision & Ease

How Date Calculator Works

Simple Steps:

Pro Tips:

Common Use Cases

Project Planning

Age Calculation

Event Countdown

Business Days

Contract Duration

Historical Research

❓ Frequently Asked Questions

🔧Technical Details & Date Arithmetic

1Date Difference Calculation Logic

Inclusive vs Exclusive Counting

Time Unit Breakdown

Calculation Example

2Business Days & Weekday Selection

Common Scenarios

How It Works

3Leap Years & Calendar Handling

Leap Year Rules

Days Per Month

4Date Addition & Subtraction

Adding Time (Future Dates)

Subtracting Time (Past Dates)

Month-End Handling

5Week Numbers & Quarter Calculations

ISO 8601 Week Numbering

Fiscal Quarters

6Time Unit Conversions

🔒Privacy & Client-Side Processing

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✗Server-Based Tools

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Frequently Asked Questions