Well here is something just for fun to determine the date. There are way too many things wrong with it, in the sense that it is not really shot in York (approximating Downton), the time by the church bells is probably not accurate, and as I understand it, most of the shooting actually occurs in the Spring. But knowing the time and the length of the shadows, and that it must be past mid year, we can approximate the date.
At about 40:35 into S4E8 (UK Version), Isobel and Lord Merton are walking past a graveyard. The church bell strikes 4 times or 4:00 PM. Looking at one of the shorter gravestones I measured that the shadow was almost exactly 3 times the height of the stone. Then solving for 3 times the height here with the following values:
Object Height 5
Date: Tuesday, 19 September, 1922 16:00
Latitude 53 58 N
Longitude 1 6 W
Timezone 0 (GMT)
Shadow Length 14.95
This Fall date gives a shadow length that is almost exactly 3 times the height of the object at 4:00 PM. The bazaar appears to have been a couple days later. Thus late September, where plus 8 months would be late May.
YMMV :)