4 free calculators
Date & Time
Calculate ages and exact durations between calendar dates.
Tools in this category
Age Calculator
Calculate your exact age from your date of birth.
Days Between Dates
Find the exact number of calendar days between two dates.
Add Days to Date Calculator
Add or subtract a whole number of calendar days from a date.
Business Days Calculator
Count Monday-to-Friday dates in an inclusive range, excluding no public holidays.
Understand the calculations
Use these focused guides and worked articles to check formulas, assumptions and practical examples.
Continue exploring
Date & Time
Understand the formula
These are the actual formulas used by the linked tools.
D = |d₂ − d₁|
A = yₙ − yᵦ − δ
Count inclusive Monday-to-Friday dates; public holidays are not excluded
Date & Time
See the numbers in practice
Use these worked examples as a reference before entering your own values.
|2026-01-31 − 2026-01-01| = 30
2026-09-01 − 2000-09-01 = 26
2026-01-05 to 2026-01-09 includes 5 Monday-to-Friday dates
Date & Time
Compare your scenarios
Keep your starting values, change one input and calculate again. Record both results to see which assumption makes the difference.
Days Between Dates