Main difference between legacy Date/Time API and Java 8 Date/Time API are:
- Old API is not Thread safe. Java 8 API is Thread safe.
- Old API has many mutable objects. New Java 8 API is based on Immutable objects.
- Performance of old API is not good. New Java 8 Date/Time API gives better performance.
- Old API is less readable and maintainable. New Java 8 API is very well designed and is more readable.
- Old API has month values from 0 to 11. New API has months from 1 to 12.