[Note: My target demographic is for a cohort over a certain age. “Keep Friday evening open, I’ll take care of the rest.” That’s a confident line, right there. You’ve now just entered the group of the top 20% of men. So you perhaps picked a happy hour at a relatively upscale place.
Of course you didn’t ask for a date, you stated it (link below).
Though replete with additional nuance, the nub of the narrative problem is easy to grasp.
Mawdryn Undead tells viewers that the Brigadier retired from UNIT in 1976.
It is further revealed that 1935 was "over forty years ago", tacitly setting The Web of Fear approximately in 1975 if not after.
The first was his debut story, The Web of Fear, when he was still a colonel in the regular British Army.
It's not particularly clear what to make of the statement.
One possibility given by The UNIT Dating Conundrum is that the entire lot of UNIT stories from Spearhead from Space to The Seeds of Doom (where the Brigadier is still in UNIT but away in Geneva) happens from 1979 to 1980; if Sarah is speaking of her "home time", i.e.
the time she (and Harry Sullivan) left with the Doctor, that would imply Planet of the Spiders, Robot, and possibly Terror of the Zygons when Harry leaves the TARDIS, would take place in 1980.
Whatever the case, her statement is not a clear violation of the continuity established by The Web of Fear.