In iOS 7, Apple completely redesigned Notification Center, and made it so that Notification Center showed the date and stock information in addition to some calendar information. The date information always shows the day, as well as the month and date.
If you would like to customize the date text in Notification Center, there's a new free jailbreak tweak available called NC Date Customizer
by iOS developer Merlin. As shown above, the tweak will let you configure the text to your liking.
The tweak will add a preferences pane to your Settings application where you can configure various options:
Here, you will find the ability to enable or disable the tweak on demand, as well as force the text to stay on a single line, or allow it to take up two line. Note: the single line text will shrink the text size so that the date information will fit on just one line. If you're hard at seeing, you may not want to enable this option.
A slider will let you choose the alignment of the text from the left side of Notification Center.
You will also find RGB color sliders, and an alpha slider for picking the color that you want the text to be, and how transparent or opaque you want the text to be.
NC Date Customizer is nice for making the date text stand out a little bit more in what is usually a bland interface with boring white text. The best part is, the tweak is absolutely free in Cydia's BigBoss repository if you want to give it a shot. The tweak can only be used on iOS 7 devices.
NC Date Cusotmizer is an open source jailbreak tweak and its source code can be viewed on GitHub here
NC Date Customizer
iPhone 5 running iOS 7.0.4