Why is it 高考那天, not 高考的天? In the following sentence:


  高考那天，我紧张极了。


I understand the meaning. But I don't understand why 那天 is used in such a way.

So why is it 高考那天, not something like 高考之天 or 高考的天 (the "of" equivalent in Mandarin)? Or 那高考的天? Is there any difference if you say it as 高考那天 or 高考的天?
天 in 那天 refers to day, so 高考那天 means the day of 高考.

天 could refer to sky too, such as 高考的天 (and 高考之天), which means the sky of 高考 and doesn't make sense. (It's same for 那高考的天, which could be literally translated as that sky of 高考.)