Methodology and sources
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.
DayTally is run by Alex, who builds simple, fast calculators for questions people search every day: how many days until a holiday, how old someone is, what a date is 90 days from now, or what an appliance costs to run.
How we build tools: every calculation runs in your browser with tested code (we keep test cases for leap years, month ends, holidays that move each year, and overnight shifts). Data such as electricity prices comes from official sources (the U.S. Energy Information Administration) and each data page states the period and source.
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