When does the US president have to be 35 year old?

Question

[The Constitution only says](https://en.wikipedia.org/wiki/Article_Two_of_the_United_States_Constitution#Clause_5:_Qualifications_for_office) that one needs to have "attained to the Age of thirty five Years" to be "eligible to the Office of President". So, do you need to have your 35th birthday: 1. On or before the first primary/caucus? 2. On or before the nomination date? 3. On or before the election date? 4. On or before the date of the College of Electors vote? 5. On or before the date of taking the oath of office? 6. Or some other step/deadline that I've missed?

Answer 1

Upon taking office, so on or before January 19 of the inauguration year.