Quick guide
How to use this calculator
- Choose the exact calendar, clock, recurrence, time-zone, working-day, or endpoint convention before entering values.
- Add one structured row for each participant, interval, stage, closure, target, or period that belongs in the scenario.
- Check the component ledger before using the headline result: it exposes skipped dates, offsets, transitions, overlaps, stage boundaries, and the convention driving the answer.
Calculation method
Explicit date and time workflow
Calendar age advances whole years and months without passing the reference date; total days use exact Gregorian ordinals.
The calculator keeps civil dates, elapsed durations, local clock readings, UTC instants, work calendars, and recurring rules distinct rather than silently treating them as interchangeable.
Worked example
Worked example
A birth date and explicit reference date produce both calendar age and total days without assuming every year has 365 days.
Calendar age advances whole years and months without passing the reference date; total days use exact Gregorian ordinals.
Supported inputs
Precision and limits
Calendar and time-zone conventions
Gregorian dates and IANA named zones are modeled explicitly. Holiday, school, legal, payroll, contractual, and operating calendars are never inferred from a country name.
DST and civil-time limits
Repeated or nonexistent local clock readings are identified where they matter. Future government time-zone changes cannot be predicted beyond the time-zone data available to the runtime.
Planning support, not authority
Results organize entered assumptions. They do not determine legal notice, payroll compliance, staffing safety, entitlement, service credits, travel feasibility, or institutional policy.
Calculator-specific boundary
This is civil calendar arithmetic, not legal age certification, biological age, developmental assessment, or a culturally specific age system.
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