Short answer
Date input = new Date();
LocalDate date = input.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
Explanation
Despite its name, java.util.Date represents an instant on the time-line, not a "date". The actual data stored within the object is a long count of milliseconds since 1970-01-01T00:00Z (midnight at the start of 1970 GMT/UTC).
The equivalent class to java.util.Date in JSR-310 is Instant, thus there is a convenient method toInstant() to provide the conversion:
Date input = new Date();
Instant instant = input.toInstant();
A java.util.Date instance has no concept of time-zone. This might seem strange if you call toString() on a java.util.Date, because the toString is relative to a time-zone. However that method actually uses Java's default time-zone on the fly to provide the string. The time-zone is not part of the actual state of java.util.Date.
An Instant also does not contain any information about the time-zone. Thus, to convert from an Instant to a local date it is necessary to specify a time-zone. This might be the default zone - ZoneId.systemDefault() - or it might be a time-zone that your application controls, such as a time-zone from user preferences. Use the atZone() method to apply the time-zone:
Date input = new Date();
Instant instant = input.toInstant();
ZonedDateTime zdt = instant.atZone(ZoneId.systemDefault());
A ZonedDateTime contains state consisting of the local date and time, time-zone and the offset from GMT/UTC. As such the date - LocalDate - can be easily extracted using toLocalDate():
Date input = new Date();
Instant instant = input.toInstant();
ZonedDateTime zdt = instant.atZone(ZoneId.systemDefault());
LocalDate date = zdt.toLocalDate();
Java 9 answer
In Java SE 9, a new method has been added that slightly simplifies this task:
Date input = new Date();
LocalDate date = LocalDate.ofInstant(input.toInstant(), ZoneId.systemDefault());
This new alternative is more direct, creating less garbage, and thus should perform better.
The Instant class represents an instantaneous point on the time-line. Conversion to and from a LocalDate requires a time-zone. Unlike some other date and time libraries, JSR-310 will not select the time-zone for you automatically, so you must provide it.
LocalDate date = LocalDate.now();
Instant instant = date.atStartOfDay(ZoneId.systemDefault()).toInstant();
This example uses the default time-zone of the JVM - ZoneId.systemDefault() - to perform the conversion. See here for a longer answer to a related question.
Update: The accepted answer uses LocalDateTime::toInstant(ZoneOffset) which only accepts ZoneOffset. This answer uses LocalDate::atStartOfDay(ZoneId) which accepts any ZoneId. As such, this answer is generally more useful (and probably should be the accepted one).
PS. I was the main author of the API
Best Answer
The way I understand it... Instant is a UTC style time, agnostic of zone always UTC. LocalTime is a time independent of given zone. So you'd expect the following would work given that
InstantimplementsTemporalAccessor,but you get "Unable to obtain LocalTime from TemporalAccessor" error. Instead you need to state where "local" is. There is no default - probably a good thing.
Output
instantStart.get(ChronoField.HOUR_OF_DAY)throws an error because it does not conceptually support it, you can only access HOUR_OF_DAY etc. via a LocalTime instance.