(1) It is past time to update your resume. [. . .]
(2) It is past time that you updated your resume.
The structure "It is past time to [infinitive clause]" is a variation of "It is time to [infinitive clause]." It is not a variation of "It is (high) time that [past tense clause]." Indeed, your example (2) does not work.
yasukotta posted:Which part of speech is the "past" in this structure?
"Past" is a preposition in "It is past time to update your resume," as can be seen by the fact that "the" is sometimes used in the construction: "It is past the time to update your resume." It is more common for "the" not to be used, however.