In this episode Radar gives Henry Blake a present of a Winchester cartridge inscribed with "To Col. Henry Blake, Korea, from Corp. O'Reilly 1952". Henry reads this inscription in its entirety including the date. There is conflict in the time line. In season 9, "A War for All Seasons" Col Potter is shown ushering in 1951 at a new years eve party. At the end of the episode he's shown ushering in 1952. Accord to this 1952 hasn't happen, yet Henry Blake died/left in 1952.
As the chopper is taking off with Col. Blake, there is a cut to Radar saluting and the rest of the officers (and Klinger) waving goodbye. After another shot of the chopper rising and flying away, a second cut to Radar, the officers, and Klinger is shown...but they are standing in a very different order from a moment before.
When Col. Blake is saying goodbye to the staff, he goes over to kiss Margaret. In the initial shot, Margaret has her right arm bent up so she can hold her hat on. The next angle, shot from behind the pair, shows Margaret's right arm over Henry's shoulder and her hand on his back. Then the view switches back to the original angle and her hand is back on her head.
Henry is being discharged because he has earned enough points. In reality, the Army stopped using the points system after World War II and doctors were never rotated according to points.
When Radar tells Henry that it is 1PM in Bloomington it would be 3 or 4AM in Korea depending on Daylight Saving Time (which Korea doesn't observe), but daylight is showing through the windows of the office.
Henry is never seen to be formally discharged from the army, and if any superiors did show up to discharge him on the day he was leaving Korea, he would've been arrested for appearing out of uniform.
When LTC Blake is saying goodbye to to the camp, Cpl. Klinger is standing in the first line of the formation. But as an enlisted man, Klinger should not be standing in the first row, which is for officers, of which there are plenty at the 4077th considering all the nurses.
Henry states that Korea is 1 day and 14 hours ahead of the United States. Radar "corrects" him by saying that it is the US that is 1 day and 14 hours ahead. However, Asia is ahead of North America.