I don't think you can set it to be there all the time with the stock settings. If you just want to see the date you can just touch and hold on the notification bar (without swiping down) the date will show up.
there are plenty of free apps to do that! DayBarWeek (I use that on my bionic and some other app on my n7 ) is just one of many. take your pick...
When you want to add a function to your android, get in the habit of cruising the Play Store. put in a search term and you'll get lots of apps to pick from.