About the Days Until Calculator
This calculator finds the span between two dates — a start date (defaulting to today) and a target date you choose — using a plain midnight-to-midnight day count. It reports the total number of calendar days, the count of business days (Monday through Friday only), the same span broken into weeks and days, and the day of the week the target date falls on.
How the calculation works
- Both dates are converted to local midnight, the difference is taken in milliseconds, then divided by 86,400,000 (the number of milliseconds in a day) and rounded to the nearest whole day.
- Business days are counted by stepping day-by-day from the start date to the target date and counting only Monday through Friday. Public holidays are not excluded, since holiday calendars vary by country and organization.
- Turning on "Count the start date as day 1" adds one extra day to the total, matching how people often count spans inclusively — Dec 1 to Dec 25 inclusive is 25 days, not 24.
Reading the result
A positive day count means the target date is still ahead of the start date; zero means the two dates are the same; a negative count means the target date has already passed relative to the start date. The business-day figure is always less than or equal to the calendar-day figure, since it strips out every Saturday and Sunday in the span.
Frequently Asked Questions
How is the number of days until a date calculated?
The calculator converts your start date and target date to local midnight, finds the difference in milliseconds, and divides by 86,400,000 (the number of milliseconds in a day), rounding to the nearest whole day. If you choose to count the start date as day 1, one extra day is added to that total.
What counts as a business day?
Business days are Monday through Friday. The calculator excludes Saturdays and Sundays from the business-day count but does not adjust for public holidays, since holiday calendars vary by country, region, and organization.
Why do the calendar-day and business-day counts differ?
Calendar days count every day in the span, while business days count only weekdays. A two-week span is 14 calendar days but only 10 business days, because it contains two weekend Saturday-Sunday pairs.
Can I calculate days until a date in the past?
Yes. If the target date is earlier than the start date, the calculator returns a negative day count and reports it as days that have already passed rather than days remaining.