Question: When did the Buddha (佛陀) die?
Answer: The Buddha did not die. He was already liberated from the cycle of birth and death (了脱生死) at the age of 35 under the Bodhi Tree (菩提树), when he accomplished Buddhahood (成佛) (i.e. Nirvāṇa: 涅槃).
Question: What about his passing later?
Answer: The Buddha did not pass away. At the age of 80, he entered Parinirvāṇa (般涅槃), which is the controlled relinquishment of his body with great ease (大自在) after concluding his teachings.
Question: Where is the Buddha now?
Answer: The Buddha continues to manifest his body (化身) with various appropriate forms in many worlds to guide sentient beings with affinity to Buddhahood.
