User blog comment:Pawn of Atlas/Important Discussion for Rapture Storyline page/@comment-75.36.142.227-20140329223049/@comment-867628-20140401143033

Often yes, but not always. And given that we know the Rapture Civil War only lasted a single year (1959) and that it began after 1958, we can certainly use those years to narrow them down somewhat; if not to exact dates then to estimated years. While some diaries do reflect bias, they also at least include verifiable facts. We know Ryan nationalized Fontaine Futuristics; not just because McDonagh said he did, but because it's also corroborated by other sources such as Ryan's diary in Bioshock 2 as well as the PA announcement.

We may have to just accept that we probably won't always have exact dates and times, but that we at least have enough to form a clear enough picture.