Re the currently low-voted answers: I would caution that if you're going to use "(?)" to indicate uncertainty in formal written English, (A) don't, and (B) be very careful about its placement.
Robinson discovered the island in 202 BC(?).
Does the writer mean that Robinson definitely discovered the island, maybe in 202 BC? Or that it's uncertain whether Robinson was the discoverer at all? Or that the writer is certain that Robinson discovered the island in 202, but isn't sure if it was BC or AD?
Robinson discovered the island in 202(?) BC.
This version reads much clearer to me personally. The "(?)" is clearly attached to the date "202"; Robinson's discovery is not in question, and neither is the fact that the "202(?)" refers to a time BC. Compare to alternatives such as
Robinson(?) discovered the island in 202 BC.
Robinson discovered the island(?) in 202 BC.
However, if you mean something, it's almost always clearer to just say that thing in English, rather than trying to encode it in the placement of punctuation.
Robinson is thought to have discovered the island in 202 BC.
The island was discovered by Robinson; Friday gives the year of its discovery as 202 BC, but other historians have contested that timeline.