How to count business days: weekends, holidays and start dates
Avoid off-by-one deadline errors by defining the workweek, start-day rule and holiday calendar before counting.
Date & time
Date & time: Practical explanations, worked examples and calculators for everyday decisions.
Days between dates: inclusive counting, nights and working days
Choose the right date-counting rule for stays, schedules and planning, with examples that explain the common one-day difference.
Leap-day birthdays: age and date calculations
Calculate elapsed time for someone born on February 29 and understand why non-leap-year birthday conventions differ.
One month from today is not always 30 days
Learn why calendar-month addition differs from a fixed day count near February and month ends.
Schedule a meeting across time zones without a date mistake
Convert a meeting hour with the correct date, check daylight saving and send an unambiguous invitation.
Calculate work shift hours with breaks and overnight time
Find payable hours when a shift crosses midnight, and separate unpaid breaks from the time on site.
Countdown between dates: when to include the start and end day
Avoid an off-by-one error when counting a deadline, hotel nights, delivery window or event countdown.
Seven business days from Friday: count with holidays and cutoffs
Work through a Friday start date while distinguishing inclusive counting, weekends and local holidays.
Business days: inclusive counts versus adding a deadline
Separate counting a date interval from moving forward a number of working days.
Adding a calendar month is not adding 30 days
Understand month-end clamping and keep calendar arithmetic separate from business-day rules.