Calculate any
date, fast.

Use the "Days between dates" tab. Enter your start and end dates and hit Calculate. The result shows total days, weeks, months, and years. You can also check "Exclude weekends" to count only business days (Monday–Friday), which is useful for project deadlines and contracts. Checking "Exclude end date" counts up to but not including the end date — how some legal and financial calculations work.

Use the "Add / subtract days" tab. Enter your starting date, the number of days, and choose whether to add or subtract. If you toggle "Skip weekends," the calculator counts only Monday–Friday — useful for business day deadlines. For example, "30 business days from today" skips Saturdays and Sundays automatically.

Use the "Day of week" tab and enter your birth date. The calculator uses JavaScript's Date object to determine the weekday with perfect accuracy for any date in the Gregorian calendar, from years 1 through 9999. Fun fact: most people's birthdays fall equally across all 7 days, but the calendar slightly favors Tuesday and Wednesday for common birth dates.

Months are calculated by counting the difference in calendar months between the two dates, adjusted for remaining days. This is an approximation — because months have different numbers of days (28–31), a "month" isn't a fixed unit like a day. For precise legal or financial purposes, always check whether the relevant agreement specifies calendar months or 30-day periods.

Set today as your start date and your target date as the end date in the "Days between dates" tab. For recurring events like birthdays and holidays, set the end date to the next occurrence. The calculator works for any date range — past, present, or future — across any year.

A business day calculator counts only weekdays (Monday through Friday), excluding Saturdays and Sundays. This is commonly needed in legal contracts ("payment due in 30 business days"), HR and employment law, shipping and logistics ("5 business days for delivery"), and court filings. This tool's weekend-exclusion option handles that automatically. Note: it does not currently account for public holidays, which vary by country and region.

Enter your last menstrual period (LMP) date as the start date and today as the end date. The days ÷ 7 gives you gestational weeks. Standard pregnancy is 40 weeks from LMP. For a dedicated due date calculator with trimester breakdown, check out our Due Date Calculator tool.