How does the calculator handle leap years and month lengths?

This calculator uses the built-in JavaScript Date object, which automatically and accurately handles all complexities related to the number of days in each month and the occurrence of leap years.

What's the difference between this and the Age Calculator?

The Age Calculator is specifically designed to output age in the common 'years, months, days' format. This Date & Time Calculator is more versatile, allowing you to add or subtract any duration (including hours and minutes) and providing a more detailed breakdown of the time interval.

Can I calculate business/working days?

No, this calculator works with calendar days only. It does not exclude weekends or public holidays. For that, you would need a specialized business day calculator.

Date & Time Calculator (Add/Subtract/Interval)

How Does This Work?

This versatile calculator handles date arithmetic with precision, accounting for all the complexities of the calendar.

Add/Subtract Duration: When you add or subtract a duration, the calculator takes your start date and sequentially modifies it. It correctly handles month lengths and leap years. For instance, adding 1 month to January 31st will result in February 28th (or 29th in a leap year), not an invalid date.
Time Between Dates: To find the interval between two dates, the calculator first determines the total number of milliseconds between them. It then intelligently breaks this massive number down into a human-readable format of years, months, days, hours, minutes, and seconds.

The Surprising History of Standardized Time

It's easy to take for granted that the time in one city is coordinated with another. But before the 1880s, this wasn't the case. Most towns set their clocks by the local sun, meaning that when it was 12:00 PM in one town, it might be 12:12 PM in a town just 300 miles east. This "local time" was a nightmare for the burgeoning railroad industry.

The solution came from a Canadian railway engineer, Sir Sandford Fleming. After missing a train due to a time mix-up, he proposed a system of worldwide, standardized time zones. His advocacy was a key driver behind the International Prime Meridian Conference of 1884 in Washington, D.C. This conference established the 24 time zones we use today, based on the Prime Meridian in Greenwich, England. It was a revolutionary change that synchronized the world and made modern global travel and communication possible.

Explore More Related Tools

While you're here, check out some of our other popular math and life event calculators:

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Frequently Asked Questions (FAQ)

Does the calculator handle time zones?

No. This calculator operates based on the local time of your device's browser. It does not perform time zone conversions. All calculations are done assuming the dates and times are in the same time zone.

How does adding "1 month" work if months have different lengths?

The calculator's underlying JavaScript `Date` object handles this smartly. If you add 1 month to January 31, it knows February doesn't have 31 days, so it will return the last day of February (the 28th or 29th). It always tries to produce a valid and logical date.

Why might the summary for "Time Between Dates" seem slightly different from the main result?

The main result (e.g., 2 years, 3 months, 5 days) is a calendar-based calculation. The summary (e.g., 795 total days) is a direct conversion from the total time difference. Because months have different lengths, the "total months" in the summary might not perfectly align with the main result, but both are correct ways of viewing the time interval.

Date & Time Calculator

Summary