Date Calculator
Find the number of days between two dates, or calculate a date by adding or subtracting days.
Start Date
End Date
Difference
365 days
Weeks
52 weeks
Months (approx.)
12 months
How to Use This Calculator
Use Days Between to find the number of days, weeks, or months between two dates. Use Add / Subtract to find a future or past date by adding or removing a number of days from a starting date. Both tabs update results instantly.
The Formula
Days Between:
Days = |Date2 − Date1| in milliseconds ÷ 86,400,000
Weeks = Days ÷ 7 (rounded down)
Add/Subtract:
Result Date = Start Date ± N days
Examples
How many days until Christmas?
Start21 March 2026
End25 December 2026
Difference279 days (39 weeks)
30 days from today
Start21 March 2026
+ 30 days20 April 2026 (Monday)
FAQ
Date calculations are essential for invoice due dates (net 30, net 60), calculating loan or credit terms, planning project deadlines, tracking contract expiry, and counting days until customs clearance or visa expiry. Nigerian importers frequently need to calculate 90-day LC payment windows and Form M validity periods.
Yes. The calculator uses JavaScript's built-in Date object which correctly handles leap years (February 29 every 4 years, except century years not divisible by 400). So 1 March 2024 minus 1 March 2023 correctly gives 366 days because 2024 is a leap year.
Common intervals: 30 days for invoices and rent payment cycles; 60 days for supplier credit terms; 90 days for quarterly reports and tax filings; 180 days for CBN Form M validity; 365 days for annual contract renewals. FIRS corporate tax returns are due 6 months after financial year end.