LS Daylock is a very beautiful LockScreen theme, featuring a minimalistic slider theme at the bottom. The LockScreen features a reflective clock widget right in the middle with running seconds. There are 4 different wallpapers that crossfade according to the time of the day. You can download this beautiful Lockscreen below.

 This is lockscreen + very simple slider package.
Wallpapers that you can see in the preview change (with an simple crossfade animation) as the clock changes, 4 wallpapers for 4 parts of the day.
On initiation of the lockscreen there is a small fade in animation from black background to the picture assigned for the current phase of the day.

You can switch between the 12h and 24h mode by editing functions.js (true for 24h mode, false for 12h mode)
var Time24 = true;

Info:
This skin was build on iPhone 4 running iOS 4.3.3
I always try to optimize both code and graphics for 3th gen and 4th gen devices
(but i cant guarantee if it will work on other devices/firmwares)