@RockItLikeRocketFuel
The earliest Easter build-up could even theoretically start is kind of up against a hard limit i.e. Christmas. And the retail sector needs a breather after January sales? Valentine's? Mother's Day?
Within the retail sector it's now just continuous from one thing to the next.
Cadburys creme eggs and mini eggs appear on Boxing Day, but Easter Eggs aren't fully on offer until after Burns Night, Chinese New Year, Valentine's Day and Mother's Day. Then it's Easter. Then St George's Day.
I can't actually think what comes next, but this year it will be the jubilee. Then Father's Day. Then 'back to school' about 5 seconds after the schools have broken up.
Once the schools have gone back, we can move onto Halloween and the first signs of the run up to Christmas, with mince pies and the walls of Quality Street etc appearing at the entrance to shops.
Then Bonfire Night hits the day after Halloween and once that's over then it's full on Christmas until the end of the year.
What surprises me writing that is that none of the main UK supermarkets have jumped onto the 'Swedish Crayfish Party' bandwagon, which would give them an excuse to push crayfish themed gatherings with associated outdoor tableware and extra booze in late August, just before they start ramping up to all the autumn selling excuses.