daymath
ISO 8601 calendar days · date-fns-shaped names · no
Date
, no time zones
npm
GitHub
README
Day (ISO 8601)
Amount
Function
addDays
subDays
addWeeks
addMonths
addYears
startOfMonth
endOfMonth
startOfWeek
endOfWeek
isWeekend
getDay
differenceInDays (vs 2026-01-01)
month-end
leap day
year 9999
+010000
Run
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