>>82180688 (OP)1/1/2025 would have been the middle point of the decade. Five years into the decade had elapsed at that point.
1/1/20 - new decade begins
1/1/21 - one year into the decade
1/1/22 - two years
1/1/23 - three years
1/1/24 - four years
1/1/25 - five years into the decade, so 50%
1/1/26 - six years
1/1/27 - seven years
1/1/28 - eight years
1/1/29 - nine years into the decade
1/1/30 - new decade begins