Patch Tuesday

Patch Tuesday (a.k.a. Update Tuesday) is an unofficial term used to refer to when Microsoft regularly releases security patches for its software products. It is widely referred to in this way by the industry. Microsoft formalized Patch Tuesday in October 2003.

Patch Tuesday occurs on the second, and sometimes fourth, Tuesday of each month in North America. As far as the integrated Windows Update (WU) function is concerned, Patch Tuesday begins at 18:00 or 17:00 UTC (10:00 PST (UTC−8) or 10:00 PDT (UTC−7). The updates show up in Download Center before they are added to WU, and the KB articles and the Technet bulletin are unlocked later.

Microsoft has a pattern of releasing a larger number of updates in even-numbered months, and fewer in odd-numbered months. Minor updates are also released outside Patch Tuesday. Daily updates consist of malware database refreshes for Windows Defender and Microsoft Security Essentials. Sometimes there is an extraordinary Patch Tuesday, two weeks after the regular Patch Tuesday. Some updates could be released at any time.

Starting with Windows 98, Microsoft included Windows Update that once installed and executed, would check for patches to Windows and its components, which Microsoft would release intermittently. With the release of Microsoft Update, this system also checks for updates for other Microsoft products, such as Microsoft Office, Visual Studio and SQL Server.

Earlier versions of Windows Update suffered from two problems:

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