LockDate is a tweak released today in Cydia that allows iDevice owners to customize the date text in the LockScreen. More precisely, instead of the text that tells you what date you are, you can write anything else you want or alternatively you can change the color or the font of the writing displayed there. LockDate has a dedicated menu in the Settings application of iOS and there you can customize the displayed text by choosing the color, font and words plus much more, so you can customize everything as you wish.
LockDate is available for free in Cydia.
