Days until a date
We count calendar days from today up to the target date. Today counts and the target date does not, so a date one day away shows "1 day". Add one if you want to include both ends.
The live clock counts to midnight at the start of the target date in your time zone.
Weeks, months, weekdays and weekends
Weeks are whole periods of seven days. A month is complete when the same day of the month comes round again, so January 31 to February 28 counts as zero months.
Weekdays are Monday to Friday. For business days we also take out US federal holidays that fall on a weekday. We do not apply the rule that moves a weekend holiday to the nearest weekday, so treat the business-day figure as an estimate.
Weekends count each Saturday-and-Sunday pair once.
Clock times
Pages such as "how long until 8:30" count to the next 8:30, AM or PM, whichever comes first. Pages ending in AM or PM count to that time only. Pages with hours from 13 to 23 use the 24-hour clock.
Leap years and February 29
A year is a leap year when it divides by 4, except century years, which must divide by 400. February 29 birthday pages count to the next leap year.
Time zones
Zones with fixed offsets, such as Japan Standard Time, use that offset all year. Zones that change their clocks, such as Eastern Time, follow the IANA time-zone database, so the offset updates when daylight saving time starts or ends.
World tables use the offsets in force on the day you view the page.
Holiday dates
Fixed holidays use their calendar date. Floating holidays use their rule, such as the fourth Thursday of November for US Thanksgiving. Easter uses the standard Gregorian algorithm, and Good Friday and Easter Monday follow from it.
Eid al-Fitr and Eid al-Adha use the Umm al-Qura calendar, so local dates can differ by a day after moon sighting. Lunar New Year and Diwali come from published tables for 2026 to 2037.
Sleep cycles
Bedtime suggestions assume sleep cycles of 90 minutes and 15 minutes to fall asleep. Real cycles vary from person to person, so use the times as a starting point.