It looks like you just started the blog. This can sometimes happen right at first and can sometimes be caused by you changing the timezone setting in and around the postings. If you have not yet set your timezone, go to settings > general and set it to your timezone making sure to save after making the change.
Next, edit each of the posts and change the time so that they are in the right order.
Also, the YouTube in your bottom post on the main page needs to be deleted and reinserted at a smaller size. Notice how it is expanding over and into the sidebar area? That will cause major issues for you going forward. The posting area on the theme you are using is 450px wide, so the video will have to be that wide or narrower to fit properly.