How many letters does the top answer for “up to that time” have?

The most common answer is theretofore (11 letters).

Crossword clue: up to that time

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

theretofore 11 letters wn-def

up to that time

up to the present time 67% similar → yet

from that time on 50% similar → thenceforth, thereafter

unto this; up to this time; hereto. 50% similar → hereunto