Here's how to understand it:
* "Whichever" means "it doesn't matter which one" or "any one of them."
* "Later" refers to a point in time that is further in the future.
The problem is that "whichever" implies a choice between two options, while "later" refers to a point in time. This creates a mismatch in meaning.
Here's how to rephrase it correctly:
* "The one that happens later"
* "The later of the two"
* "The one that comes later"
Example:
Incorrect: "You can choose whichever later."
Correct: "You can choose the one that happens later."
In essence, "whichever later" is a grammatically incorrect way of saying "the one that happens later."