Last updated: October 23, 2026. This page explains how DayTally creates, checks and updates its calculators and guides.
Our standards
- Primary sources first. Data comes from official statistics, standards bodies or the original publisher, and each page names its source and the period covered.
- Show the working. Each calculator states its formula and assumptions, with a worked example you can verify.
- Test before publishing. Our automated tests cover leap years, month ends, holidays that move each year, overnight shifts and time-zone-safe day counts. A failing test blocks publication.
- Independence. Advertisers and affiliate partners have no say in what we publish or how a result is calculated.
Methodology
Dates are computed with exact Gregorian calendar arithmetic in UTC, so daylight-saving changes never shift a day count. Holiday dates follow the federal rules in 5 U.S.C. 6103 and the published dates of observances. Cost tools use the formula shown on each page with the inputs you enter.
Sources we use
- U.S. federal holiday rules, 5 U.S.C. 6103, and published observance dates
- U.S. Energy Information Administration (EIA), Electric Power Monthly, average residential price by state
- CDC, "About Sleep" (adult sleep guideline)
- Wang et al. (2020), Cell Systems, dog epigenetic clock
- International Cat Care, cat age chart
How content is written
Pages are researched and edited by Alex. We use software, including AI writing tools, to help draft explanations and to generate pages from structured data (for example, one page per country or per loan amount). Every figure comes from the calculator engine or a cited data set, not from a language model, and generated text is reviewed against the source before publication. Pages that would add little beyond an existing page are excluded from search indexing.
Updates and corrections
We refresh data when the publisher releases a new edition and record the date on each page. If you spot an error, please contact us; confirmed errors are corrected promptly and the page date is updated.
Limits
Calculators give estimates for general information. They are not personalised advice; see our terms of use.