If I were writing an obituary each for Simon and Piggy, the characters in the novel Lord of the Flies by William Golding, I would aim for a date around the time of the Hiroshima bomb which was dropped on Japan by the Americans near the end of the Second World War. This event is alluded to early on in the novel "they're all dead." That would give a rough date for the date of death - they probably couldn't be specific anyway as the marooned boys probably lost track of time and forgot to keep a calendar. I might choose something poetic for Simon's passing, such as 'sadly taken from us...' as this would reflect his innocent and spiritual nature. For Piggy I might gloss over the violent manner of death as it was simply too horrific to write on a tombstone. His hobbies seemed to involve a lot of reading as always had plenty of useful facts and ideas on hand.