Sources & methods.

These official pages were accessed on October 30, 2026. Access does not imply endorsement or independent professional review.

• NIST · Guide to the SI, Appendix B.8
  US customary and SI conversion factors. Source accessed 2026-10-30.
• US Naval Observatory · Leap Years
  Gregorian leap-year rule. Source accessed 2026-10-30.
• Bureau of Labor Statistics · Calculating percent changes
  Relative change formula and comparison periods. Source accessed 2026-10-30.

How the tools work

Percentages use elementary arithmetic. The BLS reference demonstrates the relative-change convention; the site does not import CPI data. Calendar calculations apply the Gregorian leap-year rule and count whole date boundaries. Conversion factors are stored in the site's source and converted through a base unit. Temperature conversion applies an offset and scale.

Editorial and software checks

The local test suite covers leap years, endpoint conventions, weekday counting, US liquid measures, temperatures, and invalid inputs. This is software validation, not an expert certification. Examples are labeled illustrative. Dates in examples do not claim that an agency or business is open.

Media credits

All diagrams and the brand mark are original SVG artwork made for this site. The homepage also uses an AI-generated conceptual workspace photograph created with OpenAI imagegen. No stock photography, external image licenses, or identifiable people are used. See the project's media manifest for individual filenames and provenance.

Publication configuration

A canonical domain, monitored contact, and hosting-specific policy review remain to be supplied by the operator. This local build intentionally uses noindex until a real site URL is configured.