I use the following formula to determine the week number for a given period. Is it possible to reset the week number when the year changes?
=INDEX(IFNA(TEXT(VLOOKUP(A2:A, {UNIQUE(FILTER(A2:A, A2:A<>" ")),SEQUENCE(COUNTUNIQUE(A2:A))}, 2, 0), "0")))
try:
=INDEX(WEEKNUM(INDEX(SPLIT(A2:A3, " - ", ),,1)))