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On Sunday, June 26, 2011 12:57:15 pm hernan gonzalez wrote: > > An instant is a point in the universal time, it's a physical concept, > unrelated to world calendars. The time point at which the man first landed > on the moon is an instant, as is the moment at which my server restarted. > It is not related to a Timezone at all. We can specified it by some > arbitrary convention (milliseconds passed since the first atomic explosion > at Hiroshima), or by some human calendar at some place/moment: for > example, the "wall date and clock used at New York". If (only if) you use > a Gregorian Calendar to specify/show a instant, you need a date, a time > and a timezone. (but you have many timezones to choose from - as you have > several calendars - a timezone is not determined by an instant). A full > datetime (date, time, timezone) implies an instant - but an instant does > not imply a timezone. > > I suggest to take a look at the Joda time API, which is one of the very few > date-time API ("key concepts") that is generally though to cover quite > completely and consistently these issues. Took you advice and looked up the Joda API definition of an instant: http://joda-time.sourceforge.net/key_instant.html "The most frequently used concept in Joda-Time is that of the instant. An Instant is defined as an instant in the datetime continuum specified as a number of milliseconds from 1970-01-01T00:00Z. This definition of milliseconds is consistent with that of the JDK in Date or Calendar. Interoperating between the two APIs is thus simple. " Look a lot like the Unix Epoch:) "Within Joda-Time an instant is represented by the ReadableInstant interface. There are four implementations of the interface provided:
We recommend the immutable implementations for general usage. " There are those pesky time zones and calendars again. -- Adrian Klaver adrian.klaver@xxxxxxxxx |
