01 / Calculator Date calculation workbench
Calculate dates without calendar guesswork.
Exact ages, spans, countdowns, and weekday estimates with visible assumptions. Last updated: October 2026
Use this when you need a clear year, month, week, and day breakdown from birth to a chosen date.
Weekends are excluded. Public holidays are not removed automatically. Both dates count.
Compared with today in your browser. February 29 birthdays use February 28 in non-leap years, with the March 1 date shown alongside.
Age on a date
Your result appears here.
Enter a birth date. Results update as you type.
Total days between
0
How to read this age
Your result summary will appear here after you run a calculation.
02 / How it works
Calendar math with the rules in plain view.
Age in Days treats inputs as calendar dates, not hidden timestamps. Months and leap years follow real calendar boundaries. The big number answers the direct question, and the note under it says how to read it.
- Calendar days
- Age and span modes count calendar-day boundaries from one date to another, then break the total into years, months, weeks, and days. Reversed dates still give a clean span.
- Inclusive or exclusive
- The main number excludes the start date. If a form says to count both the first and last day, use the inclusive figure shown under the result.
- Weekdays, not business days
- Working-day mode removes Saturdays and Sundays only. Public holidays, closures, and payroll rules need your own calendar check.
- Math, not a ruling
- The tool cannot know school cutoffs, legal ages, or eligibility rules. It gives the calendar math so you can compare it with the rule that applies. Read the disclaimer.
03 / Examples
Date calculation examples.
Start from the real question. Each worked example shows which mode to choose, how to read the result, and where an official rule takes over from calendar math.
- School cutoffHow old is a child on a cutoff date?Use age mode for the date math, then confirm eligibility with the official district rule.
- Working daysHow many business days are between dates?Start with a weekday count, then remove holidays or closure days manually.
- DeadlineHow many days are left before a deadline?Use countdown mode for planning, while keeping official deadline rules separate.
- Leap dayHow do you read a February 29 birthday?Compare nearby non-leap-year dates without turning the result into a policy ruling.
04 / Guides
A focused date reference library.
Read the guide that matches the kind of date question you are trying to answer.
- Age and birthdaysExact age guideAge-in-days totals, birthday milestones, and reference-date choices.
- Date spansDate span guideRanges, reversed dates, and planning windows without rounding away detail.
- CountdownsCountdown guideCount toward milestones and read passed dates as days since.
- Working daysWorking days guideEstimate weekday ranges, then adjust for holidays and workplace calendars.
- ReferenceMethodologyThe assumptions behind every mode, before you rely on a result.
More guides: Leap year birthdays, School cutoff dates, Project date planning, Business days and holidays, Methods reference, FAQ, or the full guide library.