Days to Years (365 days) (d to yr)

Formula

1 d = 0.00273973 yr

years (365 days) = days × 0.002739726027 — reverse: days = years (365 days) × 365

The factor is derived from the SI definitions of both units (base unit: s) as listed in NIST SP 811; results on this page are shown to 6 significant figures, the API returns up to 12.

Worked examples

• 5 d = 0.0136986 yr
• 12.5 d = 0.0342466 yr
• 100 d = 0.273973 yr

Days to years (365 days) conversion table

FAQ

How many years (365 days) are in one day?

1 d = 0.00273973 yr. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.

What is the formula to convert days to years (365 days)?

Multiply the value in days by 0.002739726027: years (365 days) = days × 0.002739726027. For example, 5 d = 0.0136986 yr.

How do I convert years (365 days) back to days?

Multiply by the inverse factor 365 (days = years (365 days) × 365), or use the years (365 days)-to-days page.

Related conversions

• Years (365 days) to days (reverse)
• Time Converter — all time units in one tool
• Hours to Minutes
• Minutes to Hours
• Minutes to Seconds
• Seconds to Minutes
• Days to Hours
• Hours to Days
• Weeks to Days
• Days to Weeks

Machine access

• API: GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=day&to_unit=year_365
• MCP: server https://tttkmbb.com/mcp, tool convert_units with {"value":5,"from_unit":"day","to_unit":"year_365"}
• Markdown: https://tttkmbb.com/conversion/days-to-years.md · JSON: https://tttkmbb.com/conversion/days-to-years.json (add ?value= for a result) · Units: /api/v1/units?quantity=time
• OpenAPI operationId: convert_units. Freshness: static. Authentication: none.

Sources

• NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors (standard)
• BIPM – The International System of Units (SI Brochure, 9th edition) (standard)
• Wikipedia – Conversion of units (reference)