∑ Zetta Calculators

Blog — Date & Time

Guides, worked examples and explainers.

Date & Time

How to Calculate Hours Between Two Times (Payroll and Timesheets)

Figuring out hours between clock-in and clock-out seems simple — until lunch breaks, overnight shifts, and decimal conversion complicate it. Here is the method.

May 5, 2026 Date & Time

How Many Working Days Are in a Month, Quarter, or Year?

Planning a budget, projecting revenue, or estimating capacity? Knowing the exact number of working days in a period is foundational. Here are the numbers.

May 4, 2026 Date & Time

Leap-Day Birthdays: When Is Your Actual Birthday?

Born on February 29? Here is how leap-day birthdays work legally and practically, including when "leaplings" celebrate in non-leap years.

May 3, 2026 Date & Time

How to Calculate Your Exact Age in Years, Months, and Days

Your age in years alone rounds off months of living. Here is how to calculate your exact age down to the day, and why the extra precision matters.

May 2, 2026 Date & Time

Due Dates and Countdowns: Practical Uses for Date Math

Date math powers everything from project deadlines to travel itineraries. Here are the most useful calculations and how to think about each one clearly.

May 1, 2026 Date & Time

How to Add or Subtract Days, Weeks, Months, and Years from a Date

Figuring out "90 days from today" or "6 months ago" seems easy — until month lengths and leap years get in the way. Here is the precise method.

Apr 30, 2026 Date & Time

How to Calculate the Number of Days Between Two Dates

Counting the days between two dates sounds trivial — until leap years, month boundaries, and inclusive counting get involved. Here is the reliable way.

Apr 29, 2026 Date & Time

Business Days vs Calendar Days: What Is the Difference?

Contracts, shipping, and legal notices often say "within X business days." Here is exactly what that means, how to count them, and when it matters.

Apr 28, 2026