Methodology

How we calculate life in days

Every comparison is based on a fixed start date and end date. We calculate the number of full calendar days between them.

People

For a person, the start date is the date of birth and the end date is the date of death. Only people whose lives are complete are included.

Events, productions and eras

For other records, we use an editorially defined beginning and ending. The exact interpretation is described in the record and supported by a source.

Leap years and time zones

Calculations use calendar dates in UTC. Leap days are included automatically. Times of day are not used unless a record specifically requires them.

Sources and verification

Production records should include a reliable source and a verification date. Estimates or disputed dates should be clearly labelled and should not be used as primary viral results.

Recognition matters

The calculator does not always select the mathematically closest record. It balances distance, global or local relevance, popularity and editorial quality so that recognizable comparisons beat obscure exact-day matches.