When Claire Ward first visits John March, she sits in his office, and we can see Holly the receptionist's desk behind Claire through the glass wall. The first time we see this shot, there is someone who is not Holly behind the desk. The next time we see the shot, Holly is at her desk, but talking to someone, although as far as we know, no one else is there.
In the beginning as John Terry's narrator is talking about his life in Providence, RI the helicopter (seen as a shadow in the flyover) is actually showing the city of Hartford, CT.
(At about 57:50) When the diary is being read during a flashback, the date of "Friday October 13, 1771" is specified. October 13, 1771 was a Sunday.
In the beginning at 12:27 when the shot scene was at the office john called his Receptionist by name as (polly) , but at 34 when he wakes up in his office, he called her as (holly) the correct name.
All of the characters pronounce "Pawtuxet" incorrectly. In Rhode Island, any location prefaced with "Paw" has the emphasis on the second syllable, e.g., pawTUCket and pawTUXet.