Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, and 2021. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: How Excel Stores Dates and Times.
Internally, Excel stores a date or time as a number. The whole part of the number (the part to the left of the decimal point) represents the number of days starting with an arbitrary starting point (typically January 1, 1900). The decimal portion (the part to the right of the decimal point) represents the time for that date. These internal representations of dates and times are often referred to as serial numbers.
To see how this works, enter the number 23 in a cell. If you have not previously formatted the cell, Excel uses the General format, displaying the number simply as 23. If you later format this cell using a date format—m/d/yy, for instance—Excel changes the display to 1/23/00, or January 23, 1900. (January 1, 1900, is 1; January 2 is 2; January 3 is 3; and so on.)
The portion to the right of the decimal point represents a fractional portion of a day. Thus, a single second would be equal to approximately 0.00001157407, since that is equal to 1 (a day) divided by 86,400 (the number of seconds in a day).
Since Excel stores dates and times as serial numbers, you can do math on them. For instance, if you wanted to determine the number of days between two dates, or the amount of time between two times, simply subtract them from each other. The result is the number of days and fractions of days between the two.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (11337) applies to Microsoft Excel 2007, 2010, 2013, 2016, 2019, and 2021. You can find a version of this tip for the older menu interface of Excel here: How Excel Stores Dates and Times.
Professional Development Guidance! Four world-class developers offer start-to-finish guidance for building powerful, robust, and secure applications with Excel. The authors show how to consistently make the right design decisions and make the most of Excel's powerful features. Check out Professional Excel Development today!
Need to understand who is using a particular workbook? There are a number of ways you can find out, as discussed in this tip.
Discover MoreExcel tries to anticipate what you want to type into a cell, particularly when it comes to entering formulas. Here are ...
Discover MoreWhen you select a range of cells, Excel normally displays the sum of those selected cells on the status bar. If the sum ...
Discover MoreFREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."
There are currently no comments for this tip. (Be the first to leave your comment—just use the simple form above!)
Got a version of Excel that uses the ribbon interface (Excel 2007 or later)? This site is for you! If you use an earlier version of Excel, visit our ExcelTips site focusing on the menu interface.
FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."
Copyright © 2026 Sharon Parq Associates, Inc.
Please Note:
This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, and 2021. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: 
Comments