Oh, yeah. That was from, what, 1968?
But really, the timeline was all over the place. When Col. Potter arrived (and Frank was still present), it was explicitly stated to be 1952. I believe that in the episode shot from the POV of a wounded soldier, we see him writing a letter dated 1953. But then there was that "year in the life" episode with Potter and Charles that was depicted as covering a span from December 31, 1950 to January 1, 1952. And there were other date references in later years that put it in '51 or so. By that point, they were successful enough that they expected to be around for a while, so they retconned it to an earlier date within the war.
Here's my MASH timeline, warts and all, based on the real Korean War :
September-October 1950 - Henry breaks ground; Trains Radar
November - Departure of Ugly John, SpearChucker and the reffed-but-unseen TV version of Duke Forrest
. Hawkeye appointed Chief Surgeon.
December - 1st Christmas
January 1951-November - Forms the bulk of Klinger's escape attempts, phony tries at types of discharge. Bulk of Burns/Houlihan reports and attempts at ousting Henry. 90% of the first 3 seasons eps take place in 1951.
December 1951 - Henry receives his discharge notice, to take effect the next month. 2nd Christmas. Trapper's notice is issued, but is lost in army mail til the next month. Potter and BJ are informed of their assignments.
New Year's, 1952 - Henry makes a toast to the New Year that Potter repeats a year later.
Early January , 1952 - Formal discharge and subsequent death of Lt. Col. Henry Blake. Hawkeye manages to get a pass to Tokyo (From Burns?). While he's gone, Trapper's delayed orders surface, and he is gone by the time Pierce gets back. Enter BJ.
Late January - Frank is relieved of command by Colonel Potter, who it should be noted, gets no reports written about him.
Over the course of
1952, Klinger begins to cross-dress less often, relying on scams for his ticket out.
June - Margaret becomes engaged, ending her affair with Frank.
July 4th - 'You Creamed IT, you NINNY!'
Late July - Hawkeye is reunited with Carlye.
Mid-Late August - Margaret marries Donald Pinobscott. Frank is given leave time, has mental breakdown. Is promoted and sent home.
Early September - Arrival of Charles. Hawkeye and Radar have falling out over his wounding; reconcile. An extended newsreel of the year's earlier Olympics causes one to be held at the 4077th. Charles makes extensive bets on baseball, not truly understanding that the season is mostly decided by that point.
November - The events of 'Comrades In Arms'. By month's end, Margaret has decided to divorce Pinobscott. BJ grows a moustache.
Early December - Margaret's short marriage ends in a final divorce. Depressed before Christmas, Hawkeye invades the peace talks. Charles' sister suffers heartbreak when her engagement is undone by ethnic bigotries.
Late December - All Christmas episodes from S4-S11 fit in here--somehow.
Early January, 1953 - Death of Edna O'Reilly's brother Edward; Radar is discharged.
Mid-January - (speculation) Finding out that Zale helped the other unit in 'Goodbye,Radar' steal their backup generator, Potter kicks him out. His sort-of replacement, Luther Rizzo, is a questionable improvement.
May - A would-be beach outing never reaches the beach. When Hawkeye sees a mother smother her newborn infant to keep it from alerting enemy patrols, the pressure of the war finally cracks Pierce, who spends time away from the 4077th recovering.
July - End of hostilities; Dissolution of 4077th MASH.
Early August - Most former members of the unit arrive home.
I'll concede it has holes. But I choose to stand by it.