How we count days
The same dates can give different answers when the counting rule changes. Each result tells you which rule it uses.
Updated
Dates and clocks are different
A day count measures calendar boundaries, not blocks of elapsed hours. A clock countdown measures time to a particular instant. Daylight saving time can change the elapsed hours without changing the number of dates.
Where holiday dates come from
US federal holiday rules come from federal law and the Office of Personnel Management. Easter follows the Gregorian calculation described by the US Naval Observatory. The data page lists the sources and the dates they were read.
What is included
Days-until counts leave today out and include the target date. Sleeps means the same number of nights before the target. Date differences include the start date and leave out the end date unless you choose to include it. Weekdays are Monday through Friday; they do not remove holidays.
Months and years keep the day of the month when it exists. Otherwise they use the last day of the target month. Calendar age counts completed years, then months, then days. A February leap-day birthday uses the last day of February in a non-leap year. This is a counting convention, not a rule for legal age.
ISO weeks start on Monday, with the first Thursday in week one. The Sunday-start comparison uses the week containing January first as week one, including dates in the previous December. There is no single week-number rule used by everyone in the US.
Working days use the selected weekend days. The US federal option follows observed closures for a standard Monday-to-Friday federal workweek. State holidays, one-off closures and employer schedules are not included. Changing the weekend does not change federal observed dates.
Today and future dates
Your browser supplies today in the timezone shown. Counts refresh when the date changes and when you return to an open tab. Astronomical seasons use saved US Naval Observatory times at minute precision. After winter starts, the next-season count continues into the following year when its dates are available. If no later season is available, the page says so and keeps the selected year's dates visible.
What these answers do not decide
The calculators do not determine court deadlines, payroll, legal age or which days your employer is open. Time-only hours count the clock interval you enter; use the dated-time mode when a daylight-saving change matters. Historical dates use the Gregorian calendar even before its local adoption.
Checking a difference
If another calendar disagrees, compare the timezone, start and end inclusion, weekend settings and actual versus observed holiday. We cannot take corrections yet.