On January 14, 2020, support for Windows Server 2008, SQL Server 2008 and Windows 7 will end. Don't let your infrastructure and applications go unprotected!

https://www.microsoft.com/en-us/cloud-platform/windows-server-2008

End of support refers to the date when Microsoft no longer provides automatic fixes, security updates, or online technical assistance. As a result, any vulnerabilities in the operating system that are discovered after this date will not be fixed by Microsoft. What’s more, Microsoft will no longer offer any type of support for the operating system meaning it won’t be long before those systems are specifically targeted and exploited.

If you haven't migrated yet, it's time for action!