http://buddhism.abou...parinirvana.htm
"Soon after he had recovered from his illness, the Lord Buddha suggested he and Ananda spend the day at a shrine, called the Capala Shrine. As the two elderly men sat together, the Buddha remarked upon the beauty of the scenery all around. The Blessed One continued, Whosoever, Ananda, has prefected psychic power could, if he so desired, remain in this place throughout a world-period or until the end of it. The Tathagata, Ananda, has done so. Therefore the Tathagata could remain throughout a world-period or until the end of it.
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The Buddha told the shaken Ananda about his decision to make his final entry into Nirvana in three months. Ananda objected, and the Buddha replied that Ananda should have made his objections known earlier, and requested the Tathagata remain throughout a world-period or until the end of it."
But for the stupid mistake of Buddha's assistant Ananda, Buddha would have lived in his body even until now.