Present Tense + Past tense with 'Since'
Incorrect : Ten years passed since he died. Or Ten years are passing since he died.
Correct : Ten years have passed since he died. Or It is ten years since he died.
Note: Formal English demands that we should use the present perfect tense with a ‘since’ clause of time.
However, the present simple tense like ‘It is ten years’ is used in informal style.