How do you calculate the exact number of days between two dates?

To calculate the exact number of days between two dates, determine the Unix epoch timestamp in milliseconds for both dates at UTC midnight, subtract the earlier timestamp from the later one, and divide the difference by 86,400,000 milliseconds (the number of milliseconds in standard 24 hours: 1000 × 60 × 60 × 24). Utilizing UTC prevents daylight saving time (DST) shifts from inadvertently skewing calculations by ±1 hour.

What is the formula for calculating business days excluding weekends?

The business days calculation excludes Saturdays (day 6) and Sundays (day 0). For an arbitrary interval between Date A and Date B, first calculate full calendar weeks: each 7-day period contributes exactly 5 working days. Then iterate through the remaining boundary days (interval modulo 7), adding 1 for each day that falls between Monday (1) and Friday (5). Optional public holiday lists are then subtracted from this subtotal.

How do you convert standard hours and minutes into decimal hours for payroll?

To convert standard hours and minutes (HH:MM) into decimal hours, keep the integer hours unchanged and divide the minutes by 60: Decimal Hours = Hours + (Minutes / 60). For example, 7 hours and 45 minutes converts to 7 + (45 / 60) = 7.75 decimal hours. For standard 15-minute payroll intervals, 1-7 minutes rounds down to .00, 8-22 minutes rounds to .25, 23-37 minutes rounds to .50, and 38-52 minutes rounds to .75.

How is the ISO week number of the year calculated?

Under the international ISO 8601 standard, a week starts on Monday, and Week 1 of any calendar year is defined as the week containing the first Thursday of January (or equivalently, the week containing January 4th). To compute the ISO week, find the Thursday of the current week; the week number is then calculated as the ordinal day of that Thursday divided by 7, rounded up. Consequently, days in late December may belong to Week 1 of the following year, or early January days may belong to Week 52 or 53 of the prior year.

TimeDateStack - Directory of Precision Date, Time & Calendar Tools

Date & Time Shift Hub

/shift/

Calculate exact future or past dates by adding or subtracting calendar days, weeks, months, or hours.

Explore Silo → Fast, Client-Side Date Shift

Duration & Span Hub

/duration/

Compute precise spans between any two dates or timestamps in days, weeks, hours, minutes, and seconds.

Explore Silo → Sub-second Precision

Age & Milestones Hub

/age/

Exact age calculation down to the minute, age gaps between partners or siblings, and life milestone trackers.

Explore Silo → Milestones & Life Events

Business & Working Days Hub

/business-days/

Exclude Saturdays, Sundays, and statutory holidays. Compute timesheet working hours and billable periods.

Explore Silo → Payroll & Settlement Math

Event & Countdown Hub

/countdown/

Live counters to milestones, holidays, weekends, seasonal equinoxes, and customized personal events.

Explore Silo → Holidays & Deadlines

Calendar & Week Math Hub

/calendar/

ISO-8601 week number standards, day number of the year (1-365/366), and leap year mathematical proof.

Explore Silo → ISO 8601 Specifications

Time Formats & Conversion Hub

/formats/

Translate between 24-hour military notation, decimal hours for payroll, and Unix timestamps.

Explore Silo → Payroll & Epoch Utilities

Time Zone & UTC Hub

/timezones/

Convert world clock differences, coordinate across global business hubs, and compute UTC offsets.

Explore Silo → Global Time Coordination

Pregnancy & Due Date Hub

/pregnancy-date/

Estimate delivery dates via Naegele's rule, track gestation weeks, and calculate trimester transitions.

Explore Silo → Gestation & Trimesters

Every Date, Time & Calendar Calculation in One Place

The 9 Core Time Hubs