Days between two dates

How the calculation works

tilwhen counts the whole calendar days between the two dates — the gap, not the span. That means the two endpoints are not both counted. If you need the duration that includes both the first and last day (for example, a hotel stay billed "Monday through Friday"), add one to the result. This is the difference between inclusive and exclusive counting, and it is the most common source of off-by-one errors.

What it's useful for

• Project and contract durations — how long a period actually runs.
• Anniversaries and milestones — days since a wedding, a birth, a job start date.
• Trip and event planning — the length of a stay or the gap before an event.
• Deadlines — how many days you have left until a fixed due date (see how to count a deadline).

Days, weeks, and business days

Alongside the total days, tilwhen shows the equivalent in weeks and days and the number of business days (Monday–Friday, weekends skipped). Business days do not exclude public holidays; see how to count business days correctly for the full method. All counting is done in your local timezone — read why that matters in date math across time zones.