Which UICollectionViewCell will be visible once scrolling finishes? Below assumes a horizontally-oriented UICollectionView.

indexPathAtEndOfScroll.m

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView
                     withVelocity:(CGPoint)velocity
              targetContentOffset:(CGPoint *)targetContentOffset {

    CGPoint point = *targetContentOffset;

    // Get point in the Center of the view
    CGPoint centerPoint = CGPointMake(point.x + CGRectGetWidth(scrollView.bounds) / 2, point.y);

    NSIndexPath *path = [self.collectionView indexPathForItemAtPoint:centerPoint];
    if (path) {
        NSDate *date = [self indexPathToDate:path]; // My app happens to convert indexPath to date. Yours probably doesn't
        DDLogWarn(@"End of scroll is: %@", [self.longDateFormatter stringFromDate:date]); // temp
    }
}