I meant if a book has start dates of 12.12.2024 [index 0] and 03.06.2025[index 1], and finished finish dates of 01.01.2025[0] and 08.07.2025[1], then the values should show:
12.12.2024-01.01.2025
03.06.2025-08.07.2025
and not in random order. 
Sorry if my original post was confusing!