Days Between Dates Calculator
Calculate the number of days, weeks, months, and years between two dates.
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About This Calculator
The Days Between Dates Calculator finds the exact number of days, weeks, months, and years between any two dates with precision and ease. Whether you're calculating project timelines, counting down to a wedding or vacation, tracking pregnancy due dates, determining employee tenure, or figuring out age in days, this tool provides instant, accurate results. Our calculator handles the complexity of varying month lengths, leap years, and the choice between including or excluding the end date—a crucial distinction for different use cases. For business applications, the workday counter excludes weekends, giving you realistic project planning timelines. The date difference calculator is essential for legal deadlines (statute of limitations, notice periods), financial calculations (Net 30/60/90 payment terms), personal milestones (anniversary countdowns, retirement planning), and educational purposes. With support for historical dates and future date calculations, this versatile tool answers the universal question: how many days are there between these two dates?
How to Use the Days Between Dates Calculator
- 1Enter the start date using the date picker or by typing in MM/DD/YYYY format.
- 2Enter the end date in the same format.
- 3View the total days between the two dates instantly.
- 4Toggle "Include end date" to add one day to the count (useful for duration calculations).
- 5Check "Exclude weekends" to see only business/working days.
- 6View the breakdown in weeks, months, and years for longer periods.
- 7Use the swap button to reverse the start and end dates quickly.
- 8For future dates, see the countdown in days, weeks, and months remaining.
How Days Are Calculated
Basic Day Count (Excluding End Date): Days = End Date - Start Date
Including End Date (for Duration): Days = (End Date - Start Date) + 1
Example: January 1 to January 10
- Excluding end date: 9 days (the span between dates)
- Including end date: 10 days (counting both first and last day)
When to Use Each Method:
- Exclude end date: Age calculations, days until an event
- Include end date: Duration of a trip (Jan 1-10 is a 10-day vacation)
Converting to Other Units:
- Weeks = Days ÷ 7
- Months = Days ÷ 30.44 (average month length)
- Years = Days ÷ 365.25 (accounting for leap years)
Leap Year Handling: Our calculator properly accounts for:
- Leap years (divisible by 4)
- Century exceptions (1900 not a leap year)
- 400-year rule (2000 was a leap year)
- February 29 dates are handled correctly
Business Days vs Calendar Days
Calendar Days: Every single day including weekends and holidays.
Business Days (Workdays): Monday through Friday, excluding weekends.
Conversion Between Them:
- 7 calendar days ≈ 5 business days
- 14 calendar days ≈ 10 business days
- 30 calendar days ≈ 21-22 business days
Business Days per Period:
| Period | Calendar Days | Business Days (Approx) |
|---|---|---|
| 1 week | 7 | 5 |
| 2 weeks | 14 | 10 |
| 1 month | 30-31 | 20-22 |
| Quarter | 90-92 | 63-66 |
| 6 months | 182-184 | 130-132 |
| 1 year | 365-366 | 260-262 |
Note About Holidays: Our business day calculation excludes weekends but not public holidays, which vary by country, state, and employer. For precise business day counts, subtract applicable holidays manually.
US Federal Holidays (11 per year): New Year's Day, MLK Day, Presidents' Day, Memorial Day, Juneteenth, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving, Christmas.
Common Date Calculations
Standard Time Periods:
| Period | Days | Business Days |
|---|---|---|
| 1 week | 7 | 5 |
| Fortnight | 14 | 10 |
| 30 days | 30 | ~21 |
| 45 days | 45 | ~32 |
| 60 days | 60 | ~43 |
| 90 days (Quarter) | 90 | ~64 |
| 120 days | 120 | ~86 |
| 6 months | ~182 | ~130 |
| 1 year | 365-366 | ~260 |
| 18 months | ~548 | ~391 |
| 2 years | 730-731 | ~521 |
| 5 years | 1,826-1,827 | ~1,304 |
| 10 years | 3,652-3,653 | ~2,608 |
Pregnancy Timeline:
- 40 weeks = 280 days from last menstrual period
- 38 weeks = 266 days from conception
- Trimesters: ~91 days each
Age Milestones in Days:
| Age | Approximate Days |
|---|---|
| 1 year | 365 |
| 18 years | 6,574 |
| 21 years | 7,670 |
| 30 years | 10,958 |
| 40 years | 14,610 |
| 50 years | 18,263 |
| 65 years | 23,741 |
| 80 years | 29,220 |
| 100 years | 36,525 |
Legal and Financial Deadlines
Payment Terms:
| Term | Meaning | Calendar Days |
|---|---|---|
| Net 10 | Payment due in 10 days | 10 |
| Net 15 | Payment due in 15 days | 15 |
| Net 30 | Payment due in 30 days | 30 |
| Net 45 | Payment due in 45 days | 45 |
| Net 60 | Payment due in 60 days | 60 |
| Net 90 | Payment due in 90 days | 90 |
| 2/10 Net 30 | 2% discount if paid in 10 days, otherwise 30 | 10 or 30 |
Legal Notice Periods:
- 3-day notice (eviction): 3 calendar days
- 7-day notice: Common for landlord repairs
- 14-day notice: Two weeks notice for resignation
- 30-day notice: Standard rental termination
- 60-day notice: Some lease terminations, WARN Act layoffs
- 90-day notice: Some contracts
Statute of Limitations (Varies by State/Country):
- Personal injury: Often 2-3 years
- Contract disputes: 4-6 years
- Medical malpractice: 1-3 years
- Tax fraud: Often no limit
- Criminal charges: Varies widely
Insurance Waiting Periods:
- Short-term disability: 7-14 days
- Long-term disability: 90-180 days
- Health insurance: Open enrollment periods
- Medicare: Specific enrollment windows
Project Management Timelines
Sprint Durations (Agile):
| Sprint Length | Calendar Days | Working Days |
|---|---|---|
| 1 week | 7 | 5 |
| 2 weeks | 14 | 10 |
| 3 weeks | 21 | 15 |
| 4 weeks | 28 | 20 |
Quarter Planning:
| Quarter | Start | End | Days |
|---|---|---|---|
| Q1 | Jan 1 | Mar 31 | 90 (91 in leap year) |
| Q2 | Apr 1 | Jun 30 | 91 |
| Q3 | Jul 1 | Sep 30 | 92 |
| Q4 | Oct 1 | Dec 31 | 92 |
Common Project Milestones:
- 30-day review
- 60-day checkpoint
- 90-day evaluation
- 6-month milestone
- Annual review (365 days)
Time Estimation Tips:
- Add 20% buffer for unexpected delays
- Use business days for work estimates
- Account for holidays during holiday seasons
- Consider team vacation schedules
- Factor in dependencies between tasks
Critical Path Method: Identify the longest sequence of dependent tasks to determine minimum project duration.
Personal Milestone Countdowns
Common Personal Countdowns:
Life Events:
- Days until wedding
- Days until due date (pregnancy)
- Days until retirement
- Days until graduation
- Days since sobriety
- Days until vacation
Anniversary Calculations:
| Anniversary | Days | Notes |
|---|---|---|
| 1 year | 365-366 | Paper |
| 5 years | ~1,826 | Wood |
| 10 years | ~3,652 | Tin |
| 25 years | ~9,131 | Silver |
| 50 years | ~18,262 | Golden |
| 60 years | ~21,915 | Diamond |
| 75 years | ~27,393 | Platinum |
Fun Day Milestones:
| Milestone | Age Equivalent |
|---|---|
| 1,000 days | ~2.7 years |
| 5,000 days | ~13.7 years |
| 10,000 days | ~27.4 years |
| 15,000 days | ~41.1 years |
| 20,000 days | ~54.8 years |
| 25,000 days | ~68.5 years |
| 30,000 days | ~82.2 years |
Birthday Day-Count Celebrations: Some people celebrate day-count birthdays like 10,000 days old instead of traditional year-based birthdays.
Historical Date Calculations
Calendar Systems:
Gregorian Calendar (Current):
- Introduced in 1582 by Pope Gregory XIII
- Replaced the Julian calendar
- Leap year rules: divisible by 4, except centuries unless divisible by 400
- Used by most of the world today
Julian Calendar (Before 1582):
- Introduced by Julius Caesar in 46 BC
- Every 4th year was a leap year (no century exception)
- Drifted ~10 days by 1582
- Still used by some Eastern Orthodox churches
When Calculating Historical Dates:
- Be aware of calendar transitions
- Different countries adopted Gregorian calendar at different times:
- Italy, Spain, Portugal: 1582
- France: 1582
- Britain and colonies: 1752 (lost 11 days)
- Russia: 1918
- Greece: 1923
Famous Date Calculations:
| Event | Days Ago (from 2026) |
|---|---|
| Moon landing (Jul 20, 1969) | ~20,650 |
| US Independence (Jul 4, 1776) | ~91,200 |
| Columbus arrival (Oct 12, 1492) | ~194,800 |
Note: Historical calculations may vary based on calendar system in use at the time.
Time Zones and Date Calculations: When calculating days across time zones:
- Use the same time zone for both dates for consistency
- International Date Line can add or subtract a day
- "Days between" typically ignores time—only dates matter
Daylight Saving Considerations:
- DST adds/removes an hour, not a full day
- Day count remains unaffected by DST changes
- When calculating hours, account for DST transitions
- Most date calculators use calendar dates only
Tip: For business purposes, always specify the time zone when scheduling deadlines across regions.
International businesses often use UTC for all deadline calculations to avoid confusion.
Month and Year Breakdown
Days in Each Month:
| Month | Days | Mnemonic |
|---|---|---|
| January | 31 | |
| February | 28/29 | Leap year: 29 |
| March | 31 | |
| April | 30 | "30 days hath September..." |
| May | 31 | |
| June | 30 | |
| July | 31 | |
| August | 31 | |
| September | 30 | |
| October | 31 | |
| November | 30 | |
| December | 31 |
Knuckle Method: Count on your knuckles and valleys. Knuckles = 31 days, valleys = 30 (except February).
Days Per Year:
- Regular year: 365 days
- Leap year: 366 days
- Average year: 365.25 days (used in calculations)
- Tropical year: 365.2422 days (actual orbit)
Cumulative Days by Month End:
| Month | Day of Year (Regular) | Day of Year (Leap) |
|---|---|---|
| January | 31 | 31 |
| February | 59 | 60 |
| March | 90 | 91 |
| April | 120 | 121 |
| May | 151 | 152 |
| June | 181 | 182 |
| July | 212 | 213 |
| August | 243 | 244 |
| September | 273 | 274 |
| October | 304 | 305 |
| November | 334 | 335 |
| December | 365 | 366 |
Pro Tips
- 💡For project planning, always use business days to get realistic timelines.
- 💡Include a buffer of 10-20% for deadline calculations to account for unexpected delays.
- 💡When counting vacation days, include both the departure and return date.
- 💡For age calculations (like "days until my birthday"), exclude the end date.
- 💡Remember that Net 30 payment terms usually mean calendar days, not business days.
- 💡Use the weeks breakdown for sprint planning in agile development.
- 💡Account for major holidays when calculating business days over holiday periods.
- 💡For long-term calculations, remember leap years add an extra day every 4 years.
- 💡The knuckle trick: knuckles are 31-day months, valleys between are 30 days.
- 💡When calculating across year boundaries, verify the total accounts for New Year.
- 💡For legal deadlines, clarify whether the first or last day is included.
- 💡Track your 10,000-day birthday—it's a unique milestone around age 27.
Frequently Asked Questions
It depends on what you're measuring. Exclude the end date for age calculations and "days until" countdowns (days until Christmas doesn't count Christmas itself). Include the end date for duration calculations like vacation length (January 1-10 is a 10-day trip if you're there on both days). Legal and financial deadlines often specify which method to use.
