Windows Azure Cloud encounters a leap year bug

The Windows Azure cloud platform encountered a global outage which lasted for hours. This was apparently due to leap year calculations.

It’s not the year 2000 bug but rather a leap year issue which affected Microsoft’s Azure cloud platform. This service allows companies to host, execute and manage applications in Microsoft’s data centre.

The widespread outage was mostly felt in the United States, lasting almost half a day on Wednesday. Other regions around the world were also affected.

The incident didn’t affect Windows Azure Storage (the storage service), and according to Microsoft only 3.8% of services hosted on Azure were impacted. Microsoft has stated that the issue was related to an interruption in the Windows Azure Compute service, which is the calculation centre.

The problem is linked to a software bug, with the causes still being analysed. It seems though that there was a calculation error based on the leap year.

Microsoft has apologised for the outage and is continuing to work through residual problems.

In 2009, Microsoft’s cloud service encountered a 22 hour outage, while in 2011, an outage at the competing Amazon Web Services last days in the United States.