Calculators
Date Calculator
Add or subtract days, weeks, months, or years from any date. Calculate business days, count days between dates, and find specific dates for planning and scheduling.
Use Date Calculator to get instant results without uploads or sign-ups. Everything runs securely in your browser for fast, reliable output.
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About this tool
Date calculations are essential for project management, contract terms, loan payoffs, pregnancy due dates, age calculations, and everyday planning. Our Date Calculator handles three main functions: (1) Adding time to a date - find what date is 90 days from now, (2) Subtracting time from a date - what date was 6 months ago, and (3) Finding the difference between two dates - how many days from today until Christmas. The calculator accounts for varying month lengths, leap years, and optionally excludes weekends for business day calculations.
Understanding date arithmetic is more complex than it seems. Adding "1 month" to January 31st could mean February 28th (or 29th in leap years) since February has fewer days. Our calculator handles these edge cases intelligently. Leap years occur every 4 years (2024, 2028) except century years not divisible by 400 (1900 wasn't a leap year, but 2000 was). This affects calculations spanning February in leap years. The calculator automatically accounts for leap years, ensuring accurate results for any date range.
Business day calculations are crucial for contracts, legal deadlines, and project management. Most businesses operate Monday-Friday, excluding weekends. If a contract states "30 business days," that's actually 42 calendar days (30 weekdays + 2 weekends). Our calculator can compute both calendar days and business days. For example, "net 30" invoice terms typically mean 30 calendar days, but some industries use 30 business days. Understanding this difference is critical - missing a business day deadline because you counted calendar days can have expensive consequences in legal or financial contexts.
The calculator is invaluable for planning: (1) Project deadlines - if project starts March 1 and takes 45 business days, when does it complete? (2) Age calculations - exactly how many days old are you? (3) Event countdowns - days until vacation, retirement, wedding. (4) Historical research - how many days between two historical events? (5) Financial calculations - maturity dates on investments, loan payoff dates. (6) Legal compliance - filing deadlines that are "X days from notice." All calculations are instant and private, performed in your browser with no data stored or transmitted.
Usage examples
Contract Payment Terms - Net 30
Invoice dated March 15, 2024, with Net 30 terms
March 15, 2024 + 30 days = April 14, 2024 (Sunday). If "Net 30" means calendar days, payment due April 14. If business days, add 30 business days: skips 8-9 weekends = approximately April 25, 2024. Always clarify whether terms are business or calendar days. Calendar day calculation is most common for invoices. Payment processed April 14 (Sunday) typically applies April 15 (Monday).
Project Deadline Planning
Project starts January 8, 2024 (Monday), needs 60 business days
January 8 + 60 business days = March 26, 2024 (Tuesday). Calculation: 60 business days requires 84 calendar days (12 weekends × 2 days). This doesn't include holidays like Presidents Day (Feb 19) or other days off. For accurate project planning, also subtract holidays: 60 business days + 1 holiday = complete by March 27. Always add buffer days for unexpected delays.
Age Calculation in Days
Person born July 15, 1990, calculating age on March 1, 2024
From July 15, 1990 to March 1, 2024 = 12,283 days (33 years, 7 months, 15 days). This includes 8 leap years (1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020), adding 8 extra days. 12,283 days ÷ 365.25 = 33.62 years. Useful for: precise age requirements (minimum ages for legal purposes), milestone celebrations, calculating compound interest periods.
Vacation Planning Countdown
Today is January 15, vacation starts June 20
January 15 to June 20 = 157 days (5 months, 5 days). Workdays remaining (excluding weekends): approximately 112 business days. Helpful for planning: vacation savings goal ($2,000 ÷ 157 days = $12.74/day to save), countdown motivation, requesting time off with adequate notice (most jobs require 30-90 days), booking flights (prices typically lowest 2-3 months before).
Legal Filing Deadline
Court notice received March 1, response due in 21 business days
March 1 + 21 business days = March 29 (Friday). Calculation: 21 business days = 29 calendar days (4 weekends). Many jurisdictions exclude the first day and include the last. If March 29 is a court holiday, deadline extends to next business day (April 1). Legal deadlines are strictly enforced - missing by one day can forfeit rights. Many attorneys set internal deadline 1-2 days early as safety buffer. Check specific jurisdiction rules: federal courts use calendar days for some deadlines, business days for others.
How to use
- Select calculation type: Add/Subtract from date or Find difference between dates
- Enter your starting date using the date picker
- For add/subtract: Enter number of days, weeks, months, or years
- Choose whether to add or subtract the time period
- Select "Business days only" to exclude weekends
- For date difference: Enter both start and end dates
- Click "Calculate" to see the result
- View results including day of week and total days
- See business days calculation excluding weekends
- Use for project planning, deadline calculation, and scheduling
Benefits
- Add or subtract days, weeks, months, or years from any date
- Calculate exact days between two dates
- Business days calculation excluding weekends
- Automatically accounts for leap years
- Handles varying month lengths correctly
- Shows day of week for calculated dates
- Perfect for project management and deadline planning
- Useful for contract terms and legal deadlines
- Calculate ages precisely in days
- No registration or personal information required
- Instant calculations with complete privacy
- Free forever with unlimited calculations
FAQs
What are business days and how are they calculated?
Business days (workdays/weekdays) are Monday through Friday, excluding weekends. "10 business days" means 10 weekdays, which spans 14 calendar days (10 weekdays + 4 weekend days). Calculation: If starting Monday and adding 10 business days, count Mon-Fri (5 days) for week 1, skip weekend, Mon-Fri (5 days) for week 2 = complete on Friday of week 2. Most business day calculations exclude only weekends, not holidays, unless specifically stated. For critical deadlines, manually subtract holidays for accuracy. International note: Some countries consider Saturday a half business day; Middle Eastern countries have Thursday-Friday weekends. Our Business Days Calculator mode automatically excludes weekends for precise workday planning.
What is a leap year and how does it affect date calculations?
Leap years have 366 days (adding Feb 29) instead of the normal 365. They occur every 4 years with exceptions: years divisible by 100 aren't leap years UNLESS also divisible by 400. Examples: 2024 is a leap year (÷4). 1900 wasn't (÷100 but not ÷400). 2000 was (÷400). Next: 2028. Leap years affect any calculation spanning February in a leap year - there's one extra day. "1 year from Jan 1, 2024" = Dec 31, 2024 (366 days in leap year). "1 year from Jan 1, 2023" = Dec 31, 2023 (365 days). For precise calculations over multiple years, leap years mean average year = 365.25 days.
When adding a month, what happens with different month lengths?
Adding "1 month" has ambiguous meaning when months have different lengths. Two approaches: (1) Same date next month: Jan 15 + 1 month = Feb 15. But Jan 31 + 1 month = Feb 28 (or 29) since Feb lacks day 31. (2) Exact days: Use average 30.44 days per month, but results land on random dates. Our calculator uses approach 1 (same date next month, or last day of month if date doesn't exist). Real-world: Most contracts use approach 1. "Payment due one month from Jan 31" = Feb 28. Rental leases: "month-to-month from Jan 31" means payment due Feb 28, Mar 31, Apr 30, May 31, etc. Always clarify "1 month" vs "30 days" in contracts - they're different!
How do I calculate my exact age in days?
Method: (Today's date) - (Birth date) = Days alive. Example: Born June 15, 1990, today is March 1, 2024. From June 15, 1990 to March 1, 2024 = 12,283 days. To calculate manually: (1) Count complete years: 33 years × 365 = 12,045 days. (2) Add leap days: 8 leap years between = +8 days. (3) Add remaining months/days: June 15 to March 1 = 259 days. Total: 12,045 + 8 + 259 = 12,312 days (approximately - exact calculation accounts for specific month lengths). Fun facts: 10,000-day birthday around age 27. 20,000-day around age 54. 30,000-day around age 82.
Does "within 30 days" include the start date?
Legal interpretation varies: (1) Exclude start date (most common): Notice dated March 1, "within 30 days" means deadline March 31 (March 2-31 = 30 days). (2) Include start date: Some jurisdictions count March 1 as day 1, deadline March 30. (3) "Within" vs "in": "Within 30 days" might mean any time before 30 days expires. "In 30 days" might mean exactly on day 30. Federal rules (FRCP): Generally exclude start date, include last day. If last day is weekend/holiday, extends to next business day. Always check specific jurisdiction or contract language. When in doubt, use earlier interpretation (March 30 instead of 31) to ensure compliance. For critical deadlines, consult attorney about specific rules.
How far in advance should I plan for important deadlines?
Buffer time recommendations by deadline type: (1) Legal/court filings: Set personal deadline 2-3 days before actual (accounts for filing problems, errors requiring correction). (2) Project deliverables: Use 10-20% buffer (60-day project plan for 54-day delivery). (3) Event planning (weddings, conferences): 6-12 months for major events. (4) Financial deadlines (taxes): File weeks early to avoid last-minute issues. (5) Rental/lease notices: Check lease (usually 30-60 days) but give landlord extra notice if possible. (6) Job notice: Professional courtesy is 2-4 weeks, but more senior roles may need 30-90 days transition. Rule of thumb: The more critical the deadline, the more buffer you need. Missing project deadline annoys clients; missing court deadline can forfeit legal rights.
What about holidays - should they be excluded from business days?
Standard business day calculations exclude only weekends (Sat-Sun), not holidays. However, practical business days should account for holidays when they matter. Federal holidays (US): New Year's, MLK Day, Presidents Day, Memorial Day, Juneteenth, July 4th, Labor Day, Columbus Day, Veterans Day, Thanksgiving, Christmas = 11 days. Some businesses close additional days (Christmas Eve, day after Thanksgiving). International: Different countries have different holidays. For critical planning: (1) Check specific industry/company holidays. (2) Manually subtract known holidays. (3) Add extra buffer days. Example: 20 business days during December = longer than usual due to Christmas/New Year closures. Government deadlines typically don't count holidays; private contracts vary - always clarify.
Can I calculate backward from a deadline?
Yes, backward calculation (subtracting) is essential for deadline planning. Example: Product launch March 31, 2024. Work backward: (1) Launch March 31. (2) Need 5 days final testing = start testing March 26. (3) Need 15 business days (3 weeks) for beta testing = start beta March 5. (4) Need 40 business days (8 weeks) for development = start dev December 26, 2023. (5) Need 20 business days for design = start design November 27, 2023. This "reverse scheduling" ensures you meet deadlines by establishing intermediate milestones. Critical path method: Identify longest task sequence, start from deadline, work backward to find latest possible start date. Always add buffer - if any step delays, the deadline slips. Use our calculator to subtract business days from deadline to find when work must start.
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