Niche D20Know a recent or historically significant event
A DC 10 Knowledge(History) can recall recent major events in history. This is not a memory of personal events, but rather commonly known major events.
Determine approximate date of an event
When a creature is already aware of an event they may attempt to get a specific date for that event via a DC 15 Knowledge(History) check.
Know a obscure or ancient historical event
A DC 20 Knowledge(History) event helps recall a historical event. This event must be one that has somehow been chronicled or passed down as otherwise beyond personal experience a character would have no other access to this knowledge.
Decipher an Exotic or Ancient text
This is usually to identify a dead language or simply read through major changes in the common tongue (the difference between modern and old english for a real life example). This can require a DC 30 Knowledge(History) check. This can potentially be even harder depending on how much information exists regarding that ancient language and may be indecipherable if no translation for the language is known/exists.
This can be a lengthy event taking 1d10+1 days to perform, requiring at least 8 hours a day spent deciphering to count towards this required time.