About the 120 Day Calculator
This tool answers a simple but easy-to-get-wrong question: what date falls 120 days — or any number of days you choose — before or after a given start date? Adding days by hand means tracking that months have different lengths (28, 29, 30, or 31 days) and that leap years insert an extra day into February. The calculator does that arithmetic on the standard Gregorian calendar automatically.
How the calculation works
- Calendar days: the end date is simply the start date plus (or minus) N days, counting every day including weekends. 120 calendar days after a date is exactly 120 × 24 hours later on the calendar.
- Business days: the calculator steps forward (or backward) one day at a time and only counts a day toward N if it falls Monday through Friday, skipping every Saturday and Sunday. Because roughly 2 of every 7 days are skipped, N business days always spans more real calendar time than N calendar days — 120 business days is about 168 calendar days, not 120.
- Public holidays are not excluded. Only weekends are skipped in business-day mode, since holiday calendars vary by country, industry, and organization.
Common uses for a 120-day calculation
- Legal and contractual deadlines that use a fixed day count, such as 120-day cure periods or notice windows
- Project and product milestones measured a fixed number of days from a kickoff date
- Warranty, return, or eligibility windows defined in calendar or business days
- Countdown and elapsed-time planning for personal or business dates
Precision note
If a deadline has legal or contractual significance, confirm the counting convention with the governing document — some rules count the start day as day 1 and some do not, and this calculator counts the start date as day 0 (the day you are adding from), matching the most common convention for "N days from" language.
Frequently Asked Questions
How do I calculate a date 120 days from today?
Set the start date to today, enter 120 for the number of days, choose "After the start date" and "Calendar days," then calculate. The tool adds 120 days on the Gregorian calendar, automatically handling different month lengths and leap years, and returns the resulting date and its day of the week.
What is the difference between calendar days and business days?
Calendar days count every day, including weekends. Business days count only Monday through Friday and skip Saturdays and Sundays. Because of that, 120 business days spans more real time than 120 calendar days — roughly 168 calendar days, since about 5 of every 7 days are business days.
Can I calculate a date before a given date instead of after?
Yes. Set the direction to "Before the start date" and the calculator subtracts the number of days instead of adding them, using the same calendar-day or business-day counting method you selected.
Does this calculator account for public holidays?
No. Business-day mode only excludes Saturdays and Sundays; it does not exclude public holidays, since holiday calendars vary by country, region, and organization. For legal or contractual deadlines that exclude specific holidays, adjust the result using the holiday calendar that applies to your situation.