In chapter 1022, Oda told us:
"Only 15 minutes remain till Onigashima reaches Flower Capital"
In this chapter, we learn that there are 5 minutes left.
I know it might not mean anything and Oda will do what he wants, but if my calculations are correct:
1022 -
15
1023 - 13
1024 - 11
1025 - 9
1026 - 7
1027 -
5
1028 - 3
1029 - 1
1030 - Whatever is going to happen to the island is going to happen in this chapter ???