Despite its huge success and staple status on the music calendar, Glastonbury is not always held annually, and since 1996 the festival organizers have taken a year off roughly every five years for various reasons.
The very first Glastonbury festival took place in 1971, but the festival did not begin to operate annually until the early 80s. In 1996 the festival organizers took their first year off to allow the land to recover after the infamous security fence breaches of 1995, when it is thought the population almost doubled after many revelers made their way into the festival site without tickets.
Similar circumstances led to the Glastonbury break of 2001, as gatecrashers had again upped the festival head-count to around 250,000 - only 100,00 tickets were officially sold - prompting public safety concerns and a refusal of another license by the local district council until the problem was resolved. The organizers used this off year to devise anti-gatecrashing measures, ensuring the safety of the festival's future in the process. The Mean Fiddler Organization was also brought in to help with their event planning expertise, and many also believe the 2001 break was also factored by the 2000 Roskilde accident in which nine crowd members died during a stage rush as Pearl Jam were playing.
2002 saw the introduction of a so called 'super fence' which discouraged gatecrashes with its unclimbable height. This ensured following festivals were some of the safest ever.
There was no Glastonbury festival in 2006, due to a scheduled break to allow land to recover and to give the organizers and much needed break. Instead, Julian Temple's documentary film 'Glastonbury' was released in its place, although had the festival had taken place, it would've been one of the best, weather wise, for years.
Glastonbury Festival has since taken place every year since then up until 2011. However, there will not be a festival in 2012 to allow the festival organizers a 'fallow' year. Head festival organizer Michael Eavis has also stated that because of the 2012 London Olympics, portaloo and policing services with either be non-existent or highly expensive as all resources are focused on the sporting event. Registration for tickets to the 2013 festival is already open.