How To Calculate Date Difference Between Two Dates In Excel

Calculate the difference between two dates in days, months, or years – just like in Excel

Complete Guide: How to Calculate Date Difference in Excel

Calculating the difference between two dates is one of the most common tasks in Excel, whether you’re tracking project timelines, calculating employee tenure, or analyzing financial periods. This comprehensive guide will show you all the methods to calculate date differences in Excel, from basic to advanced techniques.

Why Date Calculations Matter in Excel

Date calculations are fundamental in business and data analysis because:

• They help track project durations and deadlines
• Enable accurate age calculations for HR purposes
• Assist in financial modeling with time-based calculations
• Allow for precise scheduling and resource planning
• Help in calculating interest periods for loans and investments

Understanding How Excel Stores Dates

Before diving into calculations, it’s crucial to understand that Excel stores dates as sequential numbers called serial numbers. Here’s how it works:

• January 1, 1900 is stored as serial number 1
• Each subsequent day increments by 1 (January 2, 1900 = 2)
• Times are stored as fractional portions of a day (0.5 = 12:00 PM)
• This system allows Excel to perform arithmetic operations on dates

Basic Methods to Calculate Date Differences

Method 1: Simple Subtraction

The most straightforward way to find the difference between two dates is to subtract them:

1. Enter your start date in cell A1 (e.g., 1/15/2023)
2. Enter your end date in cell B1 (e.g., 5/20/2023)
3. In cell C1, enter the formula: =B1-A1
4. The result will be the number of days between the two dates

Note: The result will be in days by default. To display it in years, you’ll need to divide by 365 (or 365.25 for more accuracy).

Method 2: Using the DATEDIF Function

The DATEDIF function is specifically designed for date calculations and offers more flexibility:

Syntax: =DATEDIF(start_date, end_date, unit)

Where unit can be:

• "d" – Days
• "m" – Months
• "y" – Years
• "ym" – Months excluding years
• "yd" – Days excluding years
• "md" – Days excluding months and years

td>Months remaining after complete years

Unit	Description	Example (1/15/2020 to 5/20/2023)	Result
“d”	Complete days between dates	=DATEDIF(“1/15/2020”, “5/20/2023”, “d”)	1210
“m”	Complete months between dates	=DATEDIF(“1/15/2020”, “5/20/2023”, “m”)	40
“y”	Complete years between dates	=DATEDIF(“1/15/2020”, “5/20/2023”, “y”)	3
“ym”	=DATEDIF(“1/15/2020”, “5/20/2023”, “ym”)	4
“yd”	Days remaining after complete years	=DATEDIF(“1/15/2020”, “5/20/2023”, “yd”)	124
“md”	Days remaining after complete months	=DATEDIF(“1/15/2020”, “5/20/2023”, “md”)	5

Method 3: Using the DAYS Function (Excel 2013 and later)

For newer versions of Excel, the DAYS function provides a simple way to calculate days between dates:

Syntax: =DAYS(end_date, start_date)

Example: =DAYS("5/20/2023", "1/15/2020") returns 1210

Method 4: Using the DAYS360 Function

The DAYS360 function calculates the difference between two dates based on a 360-day year (12 months of 30 days each), which is commonly used in accounting:

Syntax: =DAYS360(start_date, end_date, [method])

The optional method parameter determines how to handle the end-of-month dates:

• FALSE or omitted: Uses US (NASD) method (default)
• TRUE: Uses European method

Advanced Date Difference Calculations

Calculating Workdays Only

To calculate the number of workdays between two dates (excluding weekends and optionally holidays), use the NETWORKDAYS function:

Basic syntax: =NETWORKDAYS(start_date, end_date)

With holidays: =NETWORKDAYS(start_date, end_date, holidays)

Example: =NETWORKDAYS("1/1/2023", "1/31/2023") returns 22 (excluding 4 weekends)

Calculating Age from Birth Date

To calculate someone’s age from their birth date, you can use a combination of functions:

=DATEDIF(birth_date, TODAY(), "y") & " years, " & DATEDIF(birth_date, TODAY(), "ym") & " months, " & DATEDIF(birth_date, TODAY(), "md") & " days"

This will return a result like “35 years, 2 months, 15 days”

Calculating Date Differences in Hours, Minutes, or Seconds

To calculate time differences in smaller units:

• Hours: =(end_date-start_date)*24
• Minutes: =(end_date-start_date)*1440
• Seconds: =(end_date-start_date)*86400

Common Errors and Troubleshooting

#VALUE! Error

This typically occurs when:

• One or both dates are not valid Excel dates
• You’re trying to subtract a later date from an earlier date (resulting in negative)
• The cell contains text instead of a date

Solution: Verify both cells contain valid dates and the end date is after the start date.

#NUM! Error

This happens when:

• You’re using DATEDIF with an invalid unit parameter
• The date is before January 1, 1900 (Excel’s earliest date)

Solution: Check your function syntax and ensure dates are within Excel’s valid range.

Incorrect Results Due to Date Formats

Sometimes cells may look like dates but are stored as text. To fix:

1. Select the problematic cells
2. Go to Data > Text to Columns
3. Click Finish to convert text to proper dates

Practical Applications of Date Differences

Project Management

Date calculations are essential for:

• Tracking project durations
• Calculating milestones and deadlines
• Monitoring task completion times
• Creating Gantt charts and timelines

Human Resources

HR departments use date calculations for:

• Calculating employee tenure
• Tracking probation periods
• Managing contract renewals
• Calculating vacation accrual

Financial Analysis

In finance, date differences help with:

• Calculating loan periods
• Determining investment horizons
• Tracking billing cycles
• Analyzing time-weighted returns

Excel Date Functions Reference

Function	Description	Example	Result
TODAY()	Returns current date	=TODAY()	Current date
NOW()	Returns current date and time	=NOW()	Current date and time
DATE(year, month, day)	Creates a date from components	=DATE(2023, 5, 20)	5/20/2023
YEAR(date)	Returns year from date	=YEAR(“5/20/2023”)	2023
MONTH(date)	Returns month from date	=MONTH(“5/20/2023”)	5
DAY(date)	Returns day from date	=DAY(“5/20/2023”)	20
EOMONTH(date, months)	Returns last day of month	=EOMONTH(“5/20/2023”, 0)	5/31/2023
WORKDAY(start_date, days, [holidays])	Returns workday after adding days	=WORKDAY(“5/20/2023”, 10)	6/5/2023

Best Practices for Date Calculations

Always Use Consistent Date Formats

Ensure all dates in your workbook use the same format to avoid calculation errors. You can standardize formats by:

• Using the Format Cells dialog (Ctrl+1)
• Applying the same date format to all relevant cells
• Using the DATE function to create dates from components

Document Your Formulas

Complex date calculations can be difficult to understand later. Add comments to explain:

• The purpose of each calculation
• Any assumptions made (like excluding holidays)
• The expected output format

Handle Leap Years Properly

For precise calculations spanning multiple years:

• Use 365.25 as the divisor when converting days to years
• Consider using the YEARFRAC function for fractional years
• Be aware of how different functions handle February 29

Validate Your Inputs

Before performing calculations:

• Use Data Validation to ensure cells contain valid dates
• Check for impossible dates (like February 30)
• Verify that end dates are after start dates

Alternative Tools for Date Calculations

Google Sheets

Google Sheets offers similar date functions with some differences:

• Uses the same DATEDIF function
• Has DAYS and DAYS360 functions
• Includes NETWORKDAYS and WORKDAY
• Handles dates slightly differently (serial numbers start at different points)

Programming Languages

For developers, here’s how to calculate date differences in other languages:

• JavaScript: const diffDays = Math.floor((date2 - date1) / (1000 * 60 * 60 * 24));
• Python: (date2 - date1).days
• PHP: $diff = date_diff($date1, $date2); echo $diff->days;
• SQL: SELECT DATEDIFF(day, '2023-01-01', '2023-05-20')

Learning Resources

For more advanced Excel date calculations, consider these authoritative resources:

• Microsoft Official DATEDIF Documentation – Comprehensive guide to the DATEDIF function directly from Microsoft
• GCFGlobal Excel Date Functions Tutorial – Free educational resource covering all Excel date functions
• IRS Publication 538 (Accounting Periods and Methods) – Official IRS document explaining accounting periods and date calculations for tax purposes

Frequently Asked Questions

Why does Excel show ###### instead of my date?

This typically happens when:

• The column isn’t wide enough to display the full date
• The cell contains a negative date or time value
• The date format is corrupted

Solution: Widen the column or check the cell’s format and value.

How do I calculate someone’s age in Excel?

Use this formula: =DATEDIF(birth_date, TODAY(), "y")

For more precision: =DATEDIF(birth_date, TODAY(), "y") & " years, " & DATEDIF(birth_date, TODAY(), "ym") & " months"

Can I calculate the difference between times in Excel?

Yes, simply subtract the start time from the end time. Format the result cell as [h]:mm:ss to display hours exceeding 24.

Example: =B1-A1 where both cells contain times

How do I exclude weekends from my date calculation?

Use the NETWORKDAYS function:

=NETWORKDAYS(start_date, end_date)

To also exclude holidays: =NETWORKDAYS(start_date, end_date, holiday_range)

Why is DATEDIF not in Excel’s function list?

DATEDIF is a legacy function that Microsoft has chosen not to document prominently, though it remains fully functional. You’ll need to type it manually as it won’t appear in the function wizard.