Excel Months Between Dates Calculator
Calculate the exact number of months between two dates using Excel’s DATEDIF function. Enter your dates below to see the result and visualization.
Complete Guide: Formula for Calculating Months Between Dates in Excel
Calculating the number of months between two dates is a common requirement in financial analysis, project management, and data reporting. While Excel doesn’t have a dedicated MONTHSBETWEEN function like some other spreadsheet software, you can achieve this using the powerful DATEDIF function or a combination of other date functions.
Understanding the DATEDIF Function
The DATEDIF function (short for “Date Difference”) is Excel’s hidden gem for calculating time differences between dates. Despite not being documented in Excel’s function library, it has been available since Excel 2000 and works reliably across all modern versions.
The function takes three arguments:
- start_date: The beginning date of the period
- end_date: The ending date of the period
- unit: The time unit to return (see table below)
| Unit | Description | Example Return Value |
|---|---|---|
| “Y” | Complete years between dates | 2 (for 2 full years) |
| “M” | Complete months between dates | 24 (for 24 full months) |
| “D” | Days between dates | 730 (for 730 days) |
| “MD” | Days difference excluding months and years | 15 (for 15 days remaining) |
| “YM” | Months difference excluding years | 3 (for 3 months remaining) |
| “YD” | Days difference excluding years | 180 (for 180 days remaining) |
Practical Examples of DATEDIF
Let’s explore some real-world scenarios where DATEDIF proves invaluable:
1. Calculating Complete Months Between Dates
To find the total number of complete months between two dates (the most common requirement):
2. Calculating Age in Years and Months
Combine multiple DATEDIF functions to get age in years and months:
3. Project Duration in Months and Days
For project management, you might want to show duration in months and remaining days:
Alternative Methods for Calculating Months Between Dates
While DATEDIF is the most straightforward method, you can also use these alternative approaches:
1. Using YEAR and MONTH Functions
This formula calculates the approximate months between dates but doesn’t account for day differences within the same month.
2. Using EDATE Function
The EDATE function can help find a date that’s a specific number of months before or after another date:
3. Using DAYS360 for Financial Calculations
For financial calculations that use a 360-day year:
Note: This divides the days by 30 to approximate months, which may not be precise for all use cases.
Common Pitfalls and How to Avoid Them
-
Date Order Matters: If your start date is after the end date, DATEDIF returns a #NUM! error. Always ensure chronological order.
=IF(A1>B1, “Invalid dates”, DATEDIF(A1, B1, “M”))
- Leap Years Consideration: DATEDIF automatically accounts for leap years in day calculations, but be aware this affects “D” and “MD” units.
-
Text vs. Date Formats: Ensure your dates are proper Excel dates, not text. Use DATEVALUE() to convert text to dates if needed.
=DATEDIF(DATEVALUE(“1/1/2020”), TODAY(), “M”)
- Negative Results: DATEDIF doesn’t return negative numbers. For dates where the day in the end date is earlier than the start date, use alternative methods.
Advanced Applications
1. Calculating Remaining Time Until a Deadline
2. Creating a Dynamic Age Calculator
Combine with TODAY() for always-up-to-date age calculations:
3. Conditional Formatting Based on Time Periods
Use DATEDIF results to apply conditional formatting rules, such as highlighting overdue projects:
- Select your date range
- Go to Home > Conditional Formatting > New Rule
- Use formula: =DATEDIF(TODAY(),A1,”D”)<0
- Set your desired format for overdue items
Performance Considerations
When working with large datasets:
- Array Formulas: For calculating months between multiple date pairs, consider array formulas to avoid helper columns.
- Volatile Functions: TODAY() is volatile (recalculates with every change). For static reports, replace with actual end dates.
- Data Types: Ensure dates are stored as proper date serial numbers, not text, for optimal performance.
Industry-Specific Applications
| Industry | Application | Example Formula |
|---|---|---|
| Finance | Loan term calculations | =DATEDIF(start_date, maturity_date, “M”) |
| HR | Employee tenure tracking | =DATEDIF(hire_date, TODAY(), “Y”) & ” years” |
| Project Management | Milestone tracking | =DATEDIF(start_date, deadline, “D”)/30 |
| Healthcare | Patient age calculations | =DATEDIF(DOB, TODAY(), “YM”) & ” months” |
| Education | Academic term durations | =DATEDIF(semester_start, semester_end, “M”) |
Excel vs. Other Tools
How month calculations compare across different platforms:
| Platform | Function | Syntax Example | Notes |
|---|---|---|---|
| Excel | DATEDIF | =DATEDIF(A1,B1,”M”) | Undocumented but reliable |
| Google Sheets | DATEDIF | =DATEDIF(A1,B1,”M”) | Same syntax as Excel |
| SQL | DATEDIFF | SELECT DATEDIFF(month, ‘2020-01-01’, ‘2022-06-01’) | Syntax varies by DBMS |
| Python | relativedelta | (end_date – start_date).days // 30 | Requires dateutil library |
| JavaScript | Custom function | monthsBetween(new Date(‘2020-01-01’), new Date(‘2022-06-01’)) | No native function |
Learning Resources
For further study on Excel date functions, consider these authoritative resources:
- Microsoft Official Documentation on DATEDIF
- Corporate Finance Institute – DATEDIF Guide
- GCFGlobal – Excel Date and Time Functions Tutorial
Frequently Asked Questions
Why doesn’t Excel document the DATEDIF function?
DATEDIF was originally included for compatibility with Lotus 1-2-3. Microsoft has kept it for backward compatibility but never officially documented it in the function library. Despite this, it’s fully supported and reliable for all calculations.
Can I use DATEDIF in Excel Online?
Yes, DATEDIF works exactly the same in Excel Online as it does in the desktop version. All the examples in this guide will work in the web version of Excel.
How do I handle dates before 1900?
Excel’s date system starts at January 1, 1900. For dates before this, you’ll need to store them as text or use a different system. The DATEDIF function won’t work with pre-1900 dates.
What’s the most accurate way to calculate months between dates?
For most business purposes, DATEDIF with the “M” unit provides the most accurate count of complete months between dates. If you need fractional months, you can combine it with day calculations:
How do I calculate months between dates excluding weekends?
For business days calculations, use NETWORKDAYS combined with month calculations: