Time Duration Calculator - Calculate Time Between Dates

Start Date & Time

Start Date

Start Time

End Date & Time

End Date

End Time

Count business days only (Mon-Fri)

Exclude weekends from hours

Duration Results

Total Duration

Years

Months

Weeks

Days

Hours

Minutes

Seconds

Additional Information

Business Days --

Weekend Days --

Working Hours (8h/day) --

Milliseconds --

Keyboard Shortcuts

Enter Calculate

Esc Reset

Ctrl + C Copy Results

D Toggle Dark Mode

How It Works

This calculator determines the exact duration between two points in time by computing the difference in milliseconds and converting it to human-readable formats. The calculation handles midnight crossovers and leap years automatically. Note that daylight saving time transitions may affect results by approximately one hour during transition periods in affected time zones.

When you enable the "Business Days Only" option, the calculator excludes weekends (Saturday and Sunday) from the day count. This is particularly useful for project planning, deadline calculations, and business scheduling where only working days matter.

The calculator stores your preferences locally, so your settings persist across sessions. All calculations are performed client-side in your browser. Year and month totals are calculated using standard averages (365.25 days per year and 30.44 days per month) and should be considered approximations for planning purposes.

Tips for Best Results

Include Seconds for Precision

For accurate billing or time tracking, include seconds in your time inputs to capture every minute of work.

Use Quick Presets

Click "Now" for the current time or use other presets to quickly set common reference points.

Business Days Calculation

Enable "Business Days Only" for project timelines that shouldn't count weekends.

Copy Results Easily

Use the copy button or Ctrl+C to quickly share duration results in documents or messages.

Frequently Asked Questions

How do I calculate time across midnight?

Simply enter the start date and time before midnight, then enter the end date (the next day) and time after midnight. The calculator automatically handles midnight crossovers and will compute the correct duration spanning multiple days.

Can I exclude weekends from my calculation?

Yes! Check the "Count business days only" checkbox to exclude Saturdays and Sundays from the day count. The Additional Information section will also show you the separate count of business days versus weekend days in your selected range.

What's the difference between elapsed time and duration?

While often used interchangeably, elapsed time typically refers to time that has passed from a past event to now, while duration refers to the length of any time span between two points. This calculator handles both—just set your start and end points accordingly.

How accurate is this calculator?

The calculator provides millisecond precision using JavaScript's Date object. It correctly handles leap years and varying month lengths. Results are accurate for any date range within JavaScript's supported range—approximately 285,616 years in either direction from January 1, 1970 (extending from 271,821 BCE to 275,760 CE). Note that month and year totals use standard averages (30.44 days/month, 365.25 days/year) and are approximate.

Can I use this for billing or invoicing?

Absolutely! The calculator shows total hours, working hours (based on 8-hour days), and business days—all commonly used for billing. Use the Copy button to transfer results to your invoices or time tracking systems. For recurring tasks, consider bookmarking with specific dates.

Why does my end time need to be after my start time?

Duration is a measure of the length of time between two points, which is inherently positive. If you accidentally swap your dates, use the "Swap" button to quickly reverse them. The calculator will also notify you if your end time is before your start time.

Does this work on mobile devices?

Yes, the calculator is fully responsive and works on all modern mobile devices and tablets. The native date and time pickers on your device will appear for easy input. Touch-friendly buttons ensure a smooth experience on smaller screens.

Are my calculations saved or stored anywhere?

All calculations happen locally in your browser—no data is sent to any server. Your preferences (like dark mode and checkbox settings) are saved to your browser's local storage for convenience, but calculation inputs are not stored. Note that local storage data is accessible to any JavaScript on this page and is not encrypted, so we only store non-sensitive preferences.

How do I handle time zones?

This calculator uses your local time zone for all calculations. If you need to calculate duration between times in different time zones, first convert both times to the same time zone before entering them. For cross-timezone calculations, consider using our Time Zone Calculator tool.

Resources & References

This calculator was built using industry-standard web technologies and follows established best practices. Below are the authoritative sources referenced during development:

MDN Web Docs: Date Object

JavaScript Date reference for accurate time calculations, parsing, and formatting.

developer.mozilla.org

W3C WCAG 2.1 Guidelines

Web Content Accessibility Guidelines ensuring this tool is usable by everyone.

w3.org

web.dev Performance

Google's guidance on building fast, efficient web applications.

web.dev

MDN: Web Storage API

Documentation for localStorage used to save your preferences locally in your browser.

developer.mozilla.org

W3C ARIA in HTML

Standards for accessible rich internet applications and screen reader support.

w3.org

ECMAScript Specification

Official JavaScript language specification for Date object behavior.

tc39.es

Disclaimer

This Time Duration Calculator is provided for informational and educational purposes only. While we strive for accuracy, the calculations should not be solely relied upon for legal, financial, medical, or other critical decisions.

The calculator uses JavaScript's Date object which operates in your local timezone and may be affected by daylight saving time transitions. For mission-critical applications requiring precise time calculations across time zones, we recommend consulting official timekeeping standards or professional services.

Business day calculations assume a standard Monday–Friday work week and do not account for public holidays, which vary by region. Users are responsible for adjusting results to account for local holidays when applicable.

Month and year duration outputs are calculated using standard average values (30.44 days per month, 365.25 days per year) and are approximations. For precise calendar-based calculations spanning specific months, manual verification is recommended.

By using this tool, you acknowledge that TimerCalculator.com and its creators are not liable for any errors, omissions, or decisions made based on the calculator's output. Always verify important calculations with multiple sources.