Digha Nikaya 1:1006
SUJATOAjja kho panānanda, rattiyā pacchime yāme kusinārāyaṁ upavattane mallānaṁ sālavane antarena yamakasālānaṁ tathāgatassa parinibbānaṁ bhavissati.
Today, Ānanda, in the last watch of the night, between a pair of sal trees in the sal forest of the Mallas at Upavattana near Kusinārā, shall be the Realized One’s full extinguishment.