[passes] or [has passed]

[ansonman]

I have made up the sentences below.

(1a) This physics formula is straightforward because it is related to a natural event. The "T" here represents the number of years that passes.

(1a) This physics formula is straightforward because it is related to a natural event. The "T" here represents the number of years that has passed.

Which tense of "pass" is correct? Thank you for your help.

[Alan]

The second makes better sense.