Chapter Eighty: Purgatorio - S5-E4
Continuity mistake: In Season 4, Archie visits his father's grave. On the grave it says May 21, 1970 - July 3, 2019, but in season 5, Veronica says "It's 2021" Veronica says this seven years after Archie visits the grave, so how has it been 7 years from 2019 to 2021?
Chapter Seventy-Nine: Graduation - S5-E3
Factual error: Archie revealed that he joined the Army to avoid repeating his senior year and was shipping to Basic Combat Training the following morning. Before leaving he would need to wait for his background and medical checks to be completed (including getting his dropped murder charge reviewed for suitability), which could take weeks. Also, the Army usually requires a diploma or GED to ship to basic. There were brief periods when the Army was accepting dropouts but it was not when this episode took place.
