Days Until Calculator

Subtract the earlier date from the later date in milliseconds, then divide by 86,400,000 (ms per day). In most spreadsheets (Excel, Google Sheets), simply subtract two date cells: =B1-A1 and format as a number. This calculator does that automatically, including business day calculation.

On average, 21-22 business days per month (Monday-Friday, excluding weekends). A standard work year has 260-261 business days (before holidays). A month with exactly 4 weeks has 20 business days. Many months have 22, and some 23. This calculator counts exact business days to your target date.

Major US holidays: New Year (Jan 1), Martin Luther King Jr Day (3rd Mon in Jan), Presidents Day (3rd Mon in Feb), Memorial Day (last Mon in May), Independence Day (Jul 4), Labor Day (1st Mon in Sep), Thanksgiving (4th Thu in Nov), Christmas (Dec 25). This calculator counts all calendar days — subtract your holidays for net business days.

Add business days to the start date. For agile sprints: count 10 business days (2 weeks) forward. For legal deadlines: use calendar days unless the rule specifies business days. For contracts: watch for terms like working days, business days, or calendar days as they lead to very different dates.

The Julian Day Number (JDN) is a continuous count of days from January 1, 4713 BC (Julian calendar). Jan 1, 2000 = JDN 2,451,545. Astronomers use it for date arithmetic across calendar systems. Modern Modified Julian Date (MJD) = JDN - 2,400,000.5, starting Nov 17, 1858.