A decade was a unit of time equal to ten years. (AUDIO: The Morton Legacy)
The Brynblaidd cannibals had a tradition of butchering travellers once every decade. (TV: Countrycide)
The Doctor spent "decades" during the latter part of his second incarnation on Darron, learning the psychic techniques of the Mind Monks. (PROSE: The Quantum Archangel)
In 1941, Jack Harkness observed that Rose Tyler was wearing fabrics that would not be around for at least another two decades. (TV: The Empty Child)
By 2008, Jack had lived on Earth for many decades. He suggested that the Saxon Master, having stolen the Doctor's TARDIS, did the same only to be told by the Tenth Doctor that he could only have travelled back as early as eighteen months prior to the present day. (TV: The Sound of Drums)
Uvlavad Kudlak, acting on the orders of the Mistres, abducted human children for decades to serve in the Uvodni's Ghost Wars against the Malakh up to 2008. (TV: Warriors of Kudlak)
In 2009, the Tenth Doctor observed that ATMOS was decades ahead of its time. (TV: The Sontaran Stratagem)
According to Jade McIntyre, Jack Robertson hated Donald Trump for decades prior to 2018. (TV: Arachnids in the UK)