Calculate the exact difference between two dates in days, weeks, months, and years. Includes business days and weekends count.
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Based on your inputs
calendar days
| Total Days | 859 days |
|---|---|
| Weeks + days | 122 weeks, 5 days |
| Approx. months | 28 months |
| Approx. years | 2 years |
| Business days (Mon–Fri) | 615 days |
| Weekend days | 244 days |
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Calculating the exact difference between two dates -- in days, weeks, months, or years -- is a common need for project planning, legal deadlines, contract terms, and personal milestones. This guide explains the methods and common pitfalls.
The most straightforward calculation subtracts one date from another to get total calendar days:
Days = (End Date - Start Date)
For example, from January 1, 2025 to March 15, 2025 = 31 (Jan) + 28 (Feb) + 15 (Mar) = 73 days. In a leap year, February has 29 days, making it 74.
Business days (Monday through Friday, excluding weekends) are critical for legal deadlines, shipping estimates, and project timelines:
73 calendar days: approximately 52 business days (depends on starting day of week)
30 calendar days: approximately 22 business days
90 calendar days: approximately 64 business days
365 calendar days: approximately 261 business days
Note: public holidays are not deducted in standard business day counts because they vary by country and region.
Many legal contexts specify deadlines in calendar days, not business days. Common examples:
Real estate: Inspection periods (typically 10-14 calendar days), financing contingencies (30-45 days)
Insurance claims: Filing deadlines often 30-90 calendar days from incident
Warranty periods: Usually 365 calendar days (1 year) from purchase
Once you know the total days, convert to other units:
Weeks = Days / 7
Months (approximate) = Days / 30.44
Years (approximate) = Days / 365.25
For precise month and year counts that respect calendar boundaries, use our date difference calculator. For simpler day counting, try the days between dates tool.
Q1 (Jan 1 - Mar 31): 90 days | Q2 (Apr 1 - Jun 30): 91 days
Q3 (Jul 1 - Sep 30): 92 days | Q4 (Oct 1 - Dec 31): 92 days
Full year: 365 days (366 in leap year) | Half year: 182-183 days
Counting business days -- the Monday-through-Friday working days between two dates -- is essential for shipping estimates, legal deadlines, payroll calculations, and project management. This guide explains how to count business days accurately.
To count business days between two dates:
Step 1: Count total calendar days between the two dates.
Step 2: Count the number of complete weeks (divide by 7). Each complete week has 5 business days.
Step 3: For remaining days, count Monday through Friday only.
Step 4: Add the complete week business days and remaining business days.
The number of business days varies by month depending on which days fall on weekends:
Minimum: 20 business days in a month
Maximum: 23 business days in a month
Average: 21.7 business days per month
Annual total: approximately 261 business days (252 after typical US holidays)
Standard shipping (5-7 business days): 7-9 calendar days
Two-week notice: 10 business days = 14 calendar days
30-day notice: Could mean 30 calendar days OR 30 business days (about 42 calendar days). Always clarify which is meant.
90-day probation: Usually 90 calendar days, about 64 business days
US federal holidays that reduce business days: New Year's Day, MLK Day, Presidents' Day, Memorial Day, Juneteenth, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving, Christmas. That is 11 days, but some may fall on weekends.
For detailed date math, use our date difference calculator which shows both calendar and business day counts. For loan or insurance deadline tracking, pair this with our date difference calculator.
Not all countries use Monday-Friday as business days. In many Middle Eastern countries, the work week runs Sunday-Thursday. In some South Asian countries, Saturday is a half-working day. Always verify the local business week when calculating international deadlines.
Calculating months and years between two dates is trickier than counting days because months have different lengths (28-31 days). This guide explains the standard methods used in finance, law, and human resources.
The most common approach counts complete calendar months:
Step 1: Count the difference in months between the two dates' month/year.
Step 2: If the end day is less than the start day, subtract one month.
Step 3: Count remaining days after the last complete month.
Example: From March 15 to July 10 = 3 months and 25 days (not 4 months). March 15 to April 15 = 1 month. April 15 to May 15 = 2 months. May 15 to June 15 = 3 months. June 15 to July 10 = 25 days.
Different conventions exist in finance:
30/360 method: Assumes every month has 30 days and every year has 360 days. Used for bond calculations and some mortgage products.
Actual/365 method: Uses actual calendar days divided by 365. Common for money market instruments.
Actual/actual method: Uses actual days in the period and actual days in the year. Most precise.
Employment duration calculations affect benefits, vacation accrual, and severance:
Probation periods: Usually 3 or 6 calendar months from start date
Service years: Counted from hire date anniversary
Notice periods: 1-3 months typically means calendar months from the notice date
Lease terms are typically stated in months. A 12-month lease starting March 15 ends on March 14 of the following year (not March 15). Some jurisdictions count differently, so check your local tenancy laws. Use our date difference calculator to verify exact lease durations and contract deadlines.
1 month = 28-31 days | 3 months = 89-92 days (1 quarter)
6 months = 181-184 days (half year) | 9 months = 273-276 days
12 months = 365-366 days | 18 months = 548-549 days
24 months = 730-731 days | 36 months = 1,095-1,096 days
Subtract the earlier date from the later date. Each day = 86,400 seconds. This calculator does it automatically.
Business days are Monday–Friday, excluding weekends. Public holidays vary by country and are not included here.
365 days in a regular year, 366 in a leap year (divisible by 4, except century years not divisible by 400).
This calculator supports any valid dates. JavaScript dates work reliably from 100 AD to 9999 AD.
Count only Monday through Friday between your start and end dates, excluding weekends. This calculator does it automatically for ranges up to 10 years. Public holidays vary by country and are not deducted.
Elapsed days count the actual number of 24-hour periods between two dates. Calendar days can mean the same thing but sometimes refers to inclusive counting where both start and end dates are counted.
Add the desired number of days to today's date. Each month has 28 to 31 days, so counting forward requires knowing the specific months involved. This calculator handles all month-length variations automatically.
Divide the total number of calendar days between the two dates by 7. The result gives complete weeks, and the remainder shows extra days beyond the last full week.
The 30/360 method assumes every month has 30 days and every year has 360 days. It simplifies interest calculations for bonds and mortgages but differs from actual calendar day counts.
Days = (Date2 − Date1) / 86,400,000 ms
Weeks = Days ÷ 7
Business days = Mon–Fri only
Every formula on this page traces to a federal agency, central bank, or peer-reviewed institution. We cite the rule-makers, not secondhand blogs.
Found an error in a formula or source? Report it →
Calculations are for educational purposes only. Consult a qualified financial advisor for personalized advice.