In an earlier conversation, Henry tells Alan that he had "been missing since Christmas" but when going through slides at the Library his "Missing Person" flyer says he was last seen January 9th.
When Josef Desjardins is talking to Henry Deaver and says he told the government to radiocarbon date his brother's finger bones - that they can tell down to the minute when they were 'lopped off' - radiocarbon dating (or radioactive carbon dating) is not that accurate, it is meant to date ancient artifacts, but there is at least a 50 year uncertainty in dating due to the fluctuation of Carbon14 in the atmosphere throughout the history of the Earth and the size of the sample taken.
In the kitchen, Ruth is cleaning some trout and says "Alan had a good day, three Brookies." The fish she has are Rainbow trout, not Brook trout.