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

Convert both dates to a common time reference (Unix timestamps or Julian day numbers), subtract the earlier from the later, then divide by the number of milliseconds in a day (86,400,000). This automatically accounts for leap years.

Does the calculator account for leap years?

Yes. Because the calculation works off actual calendar dates rather than a fixed 365-day year, leap years (which add February 29) are automatically included in any date range that spans one.

How is 'business days' different from calendar days?

Business day counts exclude Saturdays and Sundays (and optionally public holidays) from the total. A 10 calendar-day span typically contains 7-8 business days depending on which days of the week it starts and ends on.

Can I add or subtract time (not just days) from a date?

Yes — the calculator supports adding or subtracting a combination of years, months, days, hours, and minutes to any starting date/time to find the resulting date/time.

Date & Time Calculator — SmartUtilz

Name: Date & Time Calculator
Author: SmartUtilz

00:00:00

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Age Calculator

Date of Birth

Age On Date

Enter date of birth

Days Between Two Dates

Start Date

End Date

Select both dates

Add / Subtract Days from Date

Start Date

Days

Operation

Select a start date

Working Days Calculator

Start Date

End Date

Count Saturdays Count Sundays

Select both dates

Time Zone Converter

Date & Time

From Time Zone

Select date and time zone

Countdown to a Date

Event Name (optional)

Target Date & Time

Days

Hours

Minutes

Seconds

Set a target date to start countdown

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Disclaimer. This tool is provided for informational and educational purposes only. While we strive for accuracy, always independently verify date, time, and duration results before relying on them for legal, contractual, payroll, or other decision-critical purposes. Read full disclaimer →

How to Use the Date & Time Calculator

This toolkit handles everything date-related: calculate your exact age, find the difference between two dates, add or subtract days from any date, or count down to an upcoming event.

Common Use Cases

Age Calculation: Enter your date of birth to get your exact age in years, months, and days.
Project Deadlines: Add 90 days to today's date to find a Q3 deadline automatically.
Days Between Dates: Calculate how many working days remain until a contract end date.
Countdown Timer: Find how many days until a birthday, exam, or product launch.
Time Zone Conversion: Convert a meeting time across different global time zones instantly.

All calculations run locally in your browser — no data is sent to any server. Results update instantly as you type.

The Formula Behind It

Days Between = (Date₂ − Date₁) in milliseconds ÷ 86,400,000. Both dates are normalized to midnight UTC before subtracting, which is what correctly handles leap years and daylight-saving transitions without manual adjustment.

Step-by-Step Worked Example

How many days between January 15, 2026 and April 3, 2026?

Step 1: Convert both to timestamps: Jan 15 2026 00:00 UTC and Apr 3 2026 00:00 UTC.
Step 2: Subtract: difference = 78 days.
Result: 78 calendar days (which is 55 business days, excluding weekends).

Calendar Days vs. Business Days

Calendar Days	Approx. Business Days	Typical Use
7	5	One work week
30	~21-22	Notice period / 30-day payment terms
90	~64-65	Quarterly deadline
365	~260-261	Annual contract term

Date & Time Calculators

How to Use the Date & Time Calculator

Common Use Cases

The Formula Behind It

Step-by-Step Worked Example

Calendar Days vs. Business Days

Frequently Asked Questions