When Pádraic is sitting in the pub drinking by himself waiting for Colm, after he has finished his first beer, he eventually has three glasses in front of him. There are cuts back and forth between him and Siobhan as she has come looking for him. The glasses go from all three empty, to outer two empty and middle one half full, to all three empty again in three sequential cuts.
(at about 7 mins) When Pádraic picks up his pint left on the bar counter-top, the pint is half empty, but the pint was almost full when he left it on the counter-top in a scene earlier.
Early in the film, Siobhan is seen hanging the washing on the washing line outside their cottage. The white top she hangs up reverses between shots.
When Pádraic visits Colm to prove he's standing up for himself, there's a puppet on the table to Colm's left. In subsequent shots, this puppet changes position.
April 1st 1923 was not on a Friday as shown in the film.
The main characters use the term "it takes two to tango", which was originated much later in 1952, in a popular song interpreted by Pearl Bailey. However, the movie takes place in 1923 many years before the term.
The Irish Whiskey advert at the local pub is misspelled "Whisky". That's the spelling for Scotch.
The spelling is correct on the mirror. Persse's Whiskey Company of Galway used the 'Scotch' spelling on advertising mirrors and bottle labels. The business ceased before WWI, but JJ Devine's doesn't look like the sort of pub that would rush to update its wall decorations.
In the first scene in Colm's cottage, an old phonograph with a horn is seen, and heard playing a record. The record is spinning at 33 1/3 RPM, instead of 78 RPM, which was the ONLY speed used to play records in the early 1920's. The slower speed was not used until LP records were introduced in the late 1940s.
The ending drone shot of the movie has been reversed, making the ocean waves go backwards.
Pádraic says that someone needs "tough love". This concept was generated by Bill Milliken's 1968 book of the same name; it would not make much sense in 1923.
The islanders walk past a large public statue of the Virgin Mary on the way to Mass. However, in Ireland, almost all such statues were erected in the "Marian year" of 1954, or at a later date, and would not have been there in 1923.
Dominic mentions "going to church" at one point; an Irish Catholic would never use this phrase, they would instead refer to "going to Mass."