How do I calculate working days only?

A clear week is 7 days, but only 5 are working days. Over a year, weekends remove 104 days. Holidays remove another ~10. A standard work year is about 260-262 days.

What is 8.5 hours in minutes?

It is NOT 8 hours and 50 minutes. The decimal .5 represents 50% of an hour (30 minutes). So 8.5 hours = 8 hours and 30 minutes. This is a common payroll mistake.

Do you count the start date?

It depends. For 'duration', you typically calculate the difference (End - Start). If you work Monday to Friday, you worked 5 days, but Friday minus Monday equals 4 days of *difference*. Our calculator has an 'Include End Date' toggle for this reason.

Time Math: It's Harder Than You Think

"How many days until Christmas?" is easy. "How many working hours until the project deadline on March 14th?" is hard. Time is messy because our calendar is messy.

Count the Hours

Get the exact duration between any two timestamps, including or excluding weekends.

Open Time Calculator

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The "Leap Year" Trap

Everyone knows a year has 365 days. Except when it has 366.
Calculating age or duration by simply dividing days by 365 will inevitably drift over time.

Rule: Years divisible by 4 are leap years (2024, 2028).
Exception: Century years (1900, 2100) are NOT leap years unless divisible by 400 (2000 was a leap year).
If your code or manual calculation doesn't account for February 29th, your legal contracts or countdowns will be off by 24 hours.

Payroll Math: Decimal Hours vs Minutes

This is the #1 confusion for new employees filling out timesheets. Time clocks often output in Decimal Hours.

The Wrong Way

"I worked 8 hours and 50 minutes."
Writing 8.50 hours.
Result: You just shorted yourself 20 minutes of pay.

The Right Way

50 minutes / 60 minutes = 0.833.
Writing 8.83 hours.
Result: You get paid for every minute you worked.

Common Conversions

15 minutes = 0.25 hours
30 minutes = 0.50 hours
45 minutes = 0.75 hours
10 minutes = 0.166 hours

Business Days vs. Calendar Days

Calendar Days: Every day on the calendar (Mon-Sun). Used for interest calculations (car loans, credit cards) and biological events (pregnancy).

Business Days: Mon-Fri, excluding federal holidays. Used for shipping estimates ("Deliver in 3-5 days") and legal deadlines.

Tip: 10 Business Days is usually 14 Calendar Days (2 full weeks).

Interesting Date Deltas

Here are some standard durations you might need to know:

Event	Duration	Details
Full Term Pregnancy	280 Days	40 Weeks from Last Menstrual Period.
Fiscal Quarter	~91.25 Days	3 Months (Q1, Q2, Q3, Q4).
Scrum Sprint	14 Days	Standard 2-week Agile development cycle.
Mars Year	687 Days	One orbit of the Red Planet.

Conclusion

Whether you are counting down the hours to a vacation or trying to figure out if you have enough Leave Days accrued, time math is surprisingly tricky. Don't trust mental math when dates cross month boundaries (30 days vs 31 days?). Use a calculator to be sure.