On 30 June, at 23:59:60 (00:59:60 BST), the extra second was added to Coordinated Universal Time (UTC).

The slight change meant several high-profile sites which rely heavily on synchronised operations were disrupted.

Computing expert Prof Alan Woodward, from the University of Surrey, explained that the leap second can knock services out-of-sync and lead to missing data.

"Across the global internet, a lot can happen in that second," he said.

Among the affected sites was social news aggregator Reddit, which had also been hit by the storm-related problems.