some digital clocks (watches, certainly--mine does) can include seconds so you can also have 01:23:45 and 1:23:45, as well as 12:34:56.
in my lifetime, there have been two occasions of what i call "great progression".
one was 01:23:45 6/7/89 and the other was 12:34:56 7/8/90, thoguh the latter is not a "true" progression since zero is less than one. since hours cannot go above twelve (or 23) and the others 59, i don't believe you can find any more like this.
anyone else thank of any others?