Guides/Age in total days
How to calculate age in total days only
Sometimes you want one integer: “how many days old?” Newborn charts, science demos, and some contests use day totals instead of years/months.
Method
- Pick birth date and as-of date (same timezone policy for both).
- Total days = calendar difference in days (as-of − birth), usually excluding the “not yet finished” end convention your tool documents.
- Leap days between the dates are included automatically when you use real calendars —leap pitfalls.
Worked example
- Born 1 Jan 2024; as-of 1 Jan 2025 → 366 days (2024 is a leap year).
- Born 1 Jan 2023; as-of 1 Jan 2024 → 365 days.
- For Y/M/D alongside days:exact age breakdown.
Days vs completed years
Day totals answer duration; eligibility rules usually need completed years on a cutoff —cutoffs·age from DOB. Date spans generally:days between dates.