https://steemit.com/minnowbuilder/@thedarkhorse/halloween-post-winner-and-how-to-reward-old-posts

Take a look at this post. It will show you how to reward older posts.

Created the link for this post as it gets linked to daily:
https://steem-bounty.com/services/forever/@thedarkhorse/your-2-cent-vote-is-worthless-the-real-deal-on-dust-votes