Date & Time Calculators — Days, Hours & Durations

A leap year adds February 29, making the year 366 days instead of 365. Leap years occur every 4 years, except for years divisible by 100 (unless also divisible by 400). Our calculators automatically detect leap years, so dates like February 29, 2028 are handled correctly without any extra input from you.

Business days exclude Saturdays and Sundays. Our calculator counts only Monday through Friday between your two dates. For even greater accuracy, you can exclude public holidays. This is essential for legal deadlines, shipping estimates, and project management timelines.

Time zones offset local time from UTC (Coordinated Universal Time). When it is noon in New York (UTC−5), it is 5 PM in London (UTC±0) and 1 AM the next day in Tokyo (UTC+9). Our time zone converter handles these offsets, including daylight saving adjustments that shift clocks by one hour during certain months of the year.

A leap year adds an extra day (February 29) every 4 years (with exceptions: years divisible by 100 but not 400 are not leap years, e.g., 1900 no, 2000 yes).

This extra day impacts: 

• Total days between dates crossing February 29 (adds 1 day).
• Age calculations, contract durations, interest periods, and scheduling. Our date difference calculator automatically handles leap years, so you get the exact count whether the period includes Feb 29 or not.

Business days (workdays) exclude weekends (Saturday & Sunday) and optionally public holidays.

To calculate: 

1. Find total days between dates.
2. Subtract weekends.
3. Subtract any holidays that fall on weekdays. Example: From Monday to next Friday is usually 5 business days (if no holidays). Use our business days calculator — input start/end dates, toggle weekends/holidays, and get the exact count instantly (supports custom holiday lists in some versions).

Time zones affect date differences when the start and end times are in different zones or cross Daylight Saving Time (DST) changes.

Key points: 

• UTC is the reference; local times are offset (e.g., Baku +04:00).
• Crossing DST boundaries can add or subtract an hour.
• International calculations require consistent timezone handling. Our date & time duration calculator lets you specify time zones for accurate results across regions — ideal for travel, scheduling, or remote work planning.

High-quality date calculators (like ours) are very accurate for long periods because they use proper calendar rules:

• Variable month lengths (28–31 days).
• Leap years (Gregorian rule: every 4 years, skip 100 unless divisible by 400).
• No rounding errors in day counts. They remain reliable for decades or centuries (e.g., calculating days from 1900 to 2100). Always verify edge cases (Feb 29, century years) — our tool handles these automatically for exact results.