# How to use the YEARFRAC function

**What is the YEARFRAC function?**

The YEARFRAC function returns the fraction of the year based on the number of whole days between a start date and an end date. This is made possible because of how Excel handle dates.

**What is an Excel date?**

An Excel date is a serial number that Excel recognizes and can be filtered, sorted and used in other date calculations.

Excel dates are actually serial numbers formatted as dates, 1/1/1900 is 1 and 2/2/2018 is 43133. There are 43132 days between 2/2/2018 and 1/1/1900.

You can try this yourself, type 10000 in a cell, press CTRL + 1 and change the cell's formatting to date, press with left mouse button on OK. The cell now shows 5/18/1927.

**What is a year?**

A period of 365 days (366 days in leap years) based on the revolution of the Earth around the Sun. It represents one complete cycle of seasons - spring, summer, autumn, winter. Calendar years are numbered and divided into 12 months.

**What is a leap year?**

A leap year is a 366 day year occurring every 4 years to maintain calendar accuracy. A year containing an extra day, February 29th, that occurs once every 4 years.

The leap year was added to the Gregorian calendar to keep it aligned with the astronomical year. It occurs in years divisible by 4, except centurial years not divisible by 400.

**What is a fraction?**

A fraction has a numerator and a denominator:

- Numerator - The top number in a fraction.
- Denominator - The bottom number.

For example:

6/7

- The numerator is 6, meaning 6 parts.
- The denominator is 7, meaning the whole was split into 7 equal parts.

## YEARFRAC function Syntax

YEARFRAC(*start_date, end_date, [basis]*)

## YEARFRAC function Arguments

start_date |
Required. |

end_date |
Required. |

[basis] |
Optional. Day count basis.
0 - Default value. US (NASD) 30/360 1 - Actual/actual 2 - Actual/360 3 - Actual/365 4 - European 30/360 |

## YEARFRAC function example

Use the YEARFRAC function to calculate a part of a whole based on a date range relative to a year. This example demonstrates how to calculate the fraction of a year based on two specific dates located in cells C3 and C4 respectively. The [basis] argument is 0 (zero) in this example meaning it uses 30 days per month and a year has 360 days.

Formula in cell B8:

The YEARFRAC function in cell B8 returns 0.4166666 or 5/12 in fractions.

## YEARFRAC function tips

Use theÂ DATE function to create a date if you enter the date in the function.

Example:

The YEARFRAC function requires Excel dates to work properly, the DATE function allows you to create Excel dates by specifying the year, month, and day.

## YEARFRAC function not working

If using the US (NASD) 30/360 basis which is argument 0 (zero), and the *start_date* argument is the last day in February the YEARFRAC function may return an incorrect result.

The YEARFRAC function may return an incorrect result if dates are entered as text values.

YEARFRAC returns

- the #VALUE! error value if
*start_date*or*end_date*arguments are not valid dates. - the #NUM! error value if basis < 0 or if basis > 4

### 'YEARFRAC' function examples

The following article has a formula that contains the YEARFRAC function.

Table of Contents How to use the NETWORKDAYS function How to use the NETWORKDAYS.INTL function How to use the NOW […]

### Functions in 'Date and Time' category

The YEARFRAC function function is one of 22 functions in the 'Date and Time' category.

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