The problem is that handling time well is something very complex. Introducing a complex and incomplete library in std may cause misuse and/or bloat.
Java is a good example of problem. They made a simple Date object first, but since it was too naive they add Calendar later. But it was still far from perfect and complex to use. People who wanted a good time support had to use an external library(usually JodaTime). So in Java 8, Oracle has introduced a new Time API (JSR320) carefully designed based on the DateTime obejct.
So there is now 3 way of handling Date in the JavaAPI, none can be removed because of backward compatibility and most of the users still use the bad designed one.
