public class Date extends Object implements Serializable, Cloneable, Comparable<Date>
Daterepresents a specific instant in time, with millisecond precision.
Date class is intended to reflect coordinated universal time (UTC), it
may not do so exactly, depending on the host environment of the Java Virtual Machine. Nearly all
modern operating systems assume that 1 day =
24 × 60 × 60 = 86400 seconds in all cases. In UTC, however,
about once every year or two there is an extra second, called a "leap second." The leap second is
always added as the last second of the day, and always on December 31 or June 30. For example,
the last minute of the year 1995 was 61 seconds long, thanks to an added leap second. Most
computer clocks are not accurate enough to be able to reflect the leap-second distinction.
Some computer standards are defined in terms of Greenwich mean time (GMT), which is equivalent to universal time (UT). GMT is the "civil" name for the standard; UT is the "scientific" name for the same standard. The distinction between UTC and UT is that UTC is based on an atomic clock and UT is based on astronomical observations, which for all practical purposes is an invisibly fine hair to split. Because the earth's rotation is not uniform (it slows down and speeds up in complicated ways), UT does not always flow uniformly. Leap seconds are introduced as needed into UTC so as to keep UTC within 0.9 seconds of UT1, which is a version of UT with certain corrections applied. There are other time and date systems as well; for example, the time scale used by the satellite-based global positioning system (GPS) is synchronized to UTC but is not adjusted for leap seconds. An interesting source of further information is the U.S. Naval Observatory, particularly the Directorate of Time at:
and their definitions of "Systems of Time" at:
In all methods of class
Date that accept or return year, month, date, hours,
minutes, and seconds values, the following representations are used:
In all cases, arguments given to methods for these purposes need not fall within the indicated ranges; for example, a date may be specified as January 32 and is interpreted as meaning February 1.
TimeZone, Serialized Form
|Constructor and Description|
|Modifier and Type||Method and Description|
Tests if this date is after the specified date.
Tests if this date is before the specified date.
Return a copy of this object.
Compares two Dates for ordering.
Compares two dates for equality.
Returns the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this Date object.
Returns a hash code value for this object.
Dateobject and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.
public Date(long date)
Dateobject and initializes it to represent the specified number of milliseconds since the standard base time known as "the epoch", namely January 1, 1970, 00:00:00 GMT.
date- the milliseconds since January 1, 1970, 00:00:00 GMT.
public boolean after(Date when)
when- a date.
trueif and only if the instant represented by this Date object is strictly later than the instant represented by when;
public boolean before(Date when)
when- a date.
trueif and only if the instant of time represented by this Date object is strictly earlier than the instant represented by when;
public Object clone()
public int compareTo(Date anotherDate)
Dateto be compared.
0if the argument Date is equal to this Date; a value less than
0if this Date is before the Date argument; and a value greater than
0if this Date is after the Date argument.
public boolean equals(@Nullable Object obj)
trueif and only if the argument is not
nulland is a
Dateobject that represents the same point in time, to the millisecond, as this object.
Date objects are equal if and only if the
returns the same
long value for both.
public long getTime()
public int hashCode()
getTime()method. That is, the hash code is the value of the expression:
(int) (this.getTime() ˆ (this.getTime() >>> 32))
public void setTime(long time)
Dateobject to represent a point in time that is
timemilliseconds after January 1, 1970 00:00:00 GMT.
time- the number of milliseconds.
public String toString()
Dateobject to a
Stringof the form:
where:dow mon dd hh:mm:ss zzz yyyy