Date Math Basics: Calendar Days, Working Days, and Age
Date tools answer different questions: raw calendar span, business-day span, age in years/months/days, or a date shifted by an offset. This guide matches each question to the right calculator.
Calendar days vs working days
Days-between counts the calendar span using the inclusive/exclusive rule the tool documents. Working-days worksheets skip weekends and, when you enable them, holiday lists you provide—they do not invent your company’s PTO calendar.
Jurisdiction and holiday lists
Public holidays differ by country and employer. Enter the holiday set you need. These pages are not legal deadline calculators for courts or regulators.
Pick the right tool
1
Need a raw span?
Use days between dates.
2
Need business days?
Use the working days calculator with your weekend/holiday rules.
3
Need an offset date?
Use the date calculator to add or subtract days.
4
Need age?
Use the age calculator from a birth date to a reference date.