Warning: Excel provides the DATEDIF function in order to support older workbooks from Lotus 1-2-3.The DATEDIF function may calculate incorrect results under certain scenarios. Please see the known issues section of this article for further details.

How to use the SUMIFS function in Excel, one of Excel’s math and trig functions, to add arguments that meet multiple criteria.

Learn how to type a letter online using Word for the web. Choose a letter template for online letter writing. Edit, send or print your letter online.

Learn how to share Microsoft 365 Family subscription benefits with up to five people. Manage invitations, devices, and people you've shared Office with.

A Microsoft account gives you access to Microsoft products and services with just one login.

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Get the latest update for Windows 10. Windows 10 automatically downloads and installs updates to make sure your device is secure and up to date.

Learn how to create and use a VPN connection profile on Windows for secure and private internet access.

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If you get an email about unusual activity on your Microsoft account, or if you’re worried that someone else might have used your account, go to the Recent activity page.You’ll see when your Microsoft account was signed in during the last 30 days, along with any device or app-specific info.