The International Telecommunications Union (ITU)'s addition of an extra second to the Coordinated Universal Time (UTC), at the midnight hour of June 30-July 1 Greenwich Mean Time, led to the crash of a number of popular Internet services worldwide, over the weekend.

The services which witnessed glitches due to the Saturday addition of the extra second to the official timekeeping record - the adjustment marking the 25th such addition of a leap second to UTC since early 1970s - included Reddit, LinkedIn, and Quantas airline's reservation system.

With reports of crashes of Internet services - despite precautions taken by service providers - coming from all across the world, the systems for which the extra second proved to be problematic included unpatched Linux OS kernels, Java-based programs, Hadoop instances, and Cassandra databases.

According to more specific reports about the service crashes linked to the addition of the extra second, services based on servers running Debian Linux reported numerous servers going offline after the leap second occurred; while the failures reported by Reddit were essentially an upshot of its use of Java programs and the Cassandra database. Mozilla reported on leap second problems connected to Java; and the issue necessitated the company's restart of its deployments of Hadoop.

In addition, the leap second crash also caused a glitch in the reservation system for Australian airline Quantas, which went offline, and led to uptime difficulties for the LinkedIn network.