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:
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.
| Method from java.util.Date Detail: |
|---|
 public static long UTC(int year,
int month,
int date,
int hrs,
int min,
int sec) {
int y = year + 1900;
// month is 0-based. So we have to normalize month to support Long.MAX_VALUE.
if (month >= 12) {
y += month / 12;
month %= 12;
} else if (month < 0) {
y += CalendarUtils.floorDivide(month, 12);
month = CalendarUtils.mod(month, 12);
}
int m = month + 1;
BaseCalendar cal = getCalendarSystem(y);
BaseCalendar.Date udate = (BaseCalendar.Date) cal.newCalendarDate(null);
udate.setNormalizedDate(y, m, date).setTimeOfDay(hrs, min, sec, 0);
// Use a Date instance to perform normalization. Its fastTime
// is the UTC value after the normalization.
Date d = new Date(0);
d.normalize(udate);
return d.fastTime;
}
Deprecated! As - of JDK version 1.1,
replaced by Calendar.set(year + 1900, month, date,
hrs, min, sec) or GregorianCalendar(year + 1900,
month, date, hrs, min, sec), using a UTC
TimeZone, followed by Calendar.getTime().getTime().
Determines the date and time based on the arguments. The
arguments are interpreted as a year, month, day of the month,
hour of the day, minute within the hour, and second within the
minute, exactly as for the Date constructor with six
arguments, except that the arguments are interpreted relative
to UTC rather than to the local time zone. The time indicated is
returned represented as the distance, measured in milliseconds,
of that time from the epoch (00:00:00 GMT on January 1, 1970). |
public boolean after(Date when) {
return getMillisOf(this) > getMillisOf(when);
} Tests if this date is after the specified date. |
public boolean before(Date when) {
return getMillisOf(this) < getMillisOf(when);
} Tests if this date is before the specified date. |
public Object clone() {
Date d = null;
try {
d = (Date)super.clone();
if (cdate != null) {
d.cdate = (BaseCalendar.Date) cdate.clone();
}
} catch (CloneNotSupportedException e) {} // Won't happen
return d;
} Return a copy of this object. |
public int compareTo(Date anotherDate) {
long thisTime = getMillisOf(this);
long anotherTime = getMillisOf(anotherDate);
return (thisTime< anotherTime ? -1 : (thisTime==anotherTime ? 0 : 1));
} Compares two Dates for ordering. |
public boolean equals(Object obj) {
return obj instanceof Date && getTime() == ((Date) obj).getTime();
} Compares two dates for equality.
The result is true if and only if the argument is
not null and is a Date object that
represents the same point in time, to the millisecond, as this object.
Thus, two Date objects are equal if and only if the
getTime method returns the same long
value for both. |
public int getDate() {
return normalize().getDayOfMonth();
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.get(Calendar.DAY_OF_MONTH).
Returns the day of the month represented by this Date object.
The value returned is between 1 and 31
representing the day of the month that contains or begins with the
instant in time represented by this Date object, as
interpreted in the local time zone. |
public int getDay() {
return normalize().getDayOfWeek() - gcal.SUNDAY;
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.get(Calendar.DAY_OF_WEEK).
Returns the day of the week represented by this date. The
returned value (0 = Sunday, 1 = Monday,
2 = Tuesday, 3 = Wednesday, 4 =
Thursday, 5 = Friday, 6 = Saturday)
represents the day of the week that contains or begins with
the instant in time represented by this Date object,
as interpreted in the local time zone. |
public int getHours() {
return normalize().getHours();
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.get(Calendar.HOUR_OF_DAY).
Returns the hour represented by this Date object. The
returned value is a number (0 through 23)
representing the hour within the day that contains or begins
with the instant in time represented by this Date
object, as interpreted in the local time zone. |
static final long getMillisOf(Date date) {
if (date.cdate == null || date.cdate.isNormalized()) {
return date.fastTime;
}
BaseCalendar.Date d = (BaseCalendar.Date) date.cdate.clone();
return gcal.getTime(d);
} Returns the millisecond value of this Date object
without affecting its internal state. |
public int getMinutes() {
return normalize().getMinutes();
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.get(Calendar.MINUTE).
Returns the number of minutes past the hour represented by this date,
as interpreted in the local time zone.
The value returned is between 0 and 59. |
public int getMonth() {
return normalize().getMonth() - 1; // adjust 1-based to 0-based
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.get(Calendar.MONTH).
Returns a number representing the month that contains or begins
with the instant in time represented by this Date object.
The value returned is between 0 and 11,
with the value 0 representing January. |
public int getSeconds() {
return normalize().getSeconds();
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.get(Calendar.SECOND).
Returns the number of seconds past the minute represented by this date.
The value returned is between 0 and 61. The
values 60 and 61 can only occur on those
Java Virtual Machines that take leap seconds into account. |
public long getTime() {
return getTimeImpl();
} Returns the number of milliseconds since January 1, 1970, 00:00:00 GMT
represented by this Date object. |
public int getTimezoneOffset() {
int zoneOffset;
if (cdate == null) {
TimeZone tz = TimeZone.getDefaultRef();
if (tz instanceof ZoneInfo) {
zoneOffset = ((ZoneInfo)tz).getOffsets(fastTime, null);
} else {
zoneOffset = tz.getOffset(fastTime);
}
} else {
normalize();
zoneOffset = cdate.getZoneOffset();
}
return -zoneOffset/60000; // convert to minutes
} Deprecated! As - of JDK version 1.1,
replaced by -(Calendar.get(Calendar.ZONE_OFFSET) +
Calendar.get(Calendar.DST_OFFSET)) / (60 * 1000).
Returns the offset, measured in minutes, for the local time zone
relative to UTC that is appropriate for the time represented by
this Date object.
For example, in Massachusetts, five time zones west of Greenwich:
new Date(96, 1, 14).getTimezoneOffset() returns 300
because on February 14, 1996, standard time (Eastern Standard Time)
is in use, which is offset five hours from UTC; but:
new Date(96, 5, 1).getTimezoneOffset() returns 240
because on June 1, 1996, daylight saving time (Eastern Daylight Time)
is in use, which is offset only four hours from UTC.
This method produces the same result as if it computed:
(this.getTime() - UTC(this.getYear(),
this.getMonth(),
this.getDate(),
this.getHours(),
this.getMinutes(),
this.getSeconds())) / (60 * 1000)
|
public int getYear() {
return normalize().getYear() - 1900;
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.get(Calendar.YEAR) - 1900.
Returns a value that is the result of subtracting 1900 from the
year that contains or begins with the instant in time represented
by this Date object, as interpreted in the local
time zone. |
public int hashCode() {
long ht = this.getTime();
return (int) ht ^ (int) (ht > > 32);
} |
public static long parse(String s) {
int year = Integer.MIN_VALUE;
int mon = -1;
int mday = -1;
int hour = -1;
int min = -1;
int sec = -1;
int millis = -1;
int c = -1;
int i = 0;
int n = -1;
int wst = -1;
int tzoffset = -1;
int prevc = 0;
syntax:
{
if (s == null)
break syntax;
int limit = s.length();
while (i < limit) {
c = s.charAt(i);
i++;
if (c < = ' ' || c == ',')
continue;
if (c == '(') { // skip comments
int depth = 1;
while (i < limit) {
c = s.charAt(i);
i++;
if (c == '(') depth++;
else if (c == ')')
if (--depth < = 0)
break;
}
continue;
}
if ('0' < = c && c < = '9') {
n = c - '0';
while (i < limit && '0' < = (c = s.charAt(i)) && c < = '9') {
n = n * 10 + c - '0';
i++;
}
if (prevc == '+' || prevc == '-' && year != Integer.MIN_VALUE) {
// timezone offset
if (n < 24)
n = n * 60; // EG. "GMT-3"
else
n = n % 100 + n / 100 * 60; // eg "GMT-0430"
if (prevc == '+') // plus means east of GMT
n = -n;
if (tzoffset != 0 && tzoffset != -1)
break syntax;
tzoffset = n;
} else if (n >= 70)
if (year != Integer.MIN_VALUE)
break syntax;
else if (c < = ' ' || c == ',' || c == '/' || i >= limit)
// year = n < 1900 ? n : n - 1900;
year = n;
else
break syntax;
else if (c == ':')
if (hour < 0)
hour = (byte) n;
else if (min < 0)
min = (byte) n;
else
break syntax;
else if (c == '/')
if (mon < 0)
mon = (byte) (n - 1);
else if (mday < 0)
mday = (byte) n;
else
break syntax;
else if (i < limit && c != ',' && c > ' ' && c != '-')
break syntax;
else if (hour >= 0 && min < 0)
min = (byte) n;
else if (min >= 0 && sec < 0)
sec = (byte) n;
else if (mday < 0)
mday = (byte) n;
// Handle two-digit years < 70 (70-99 handled above).
else if (year == Integer.MIN_VALUE && mon >= 0 && mday >= 0)
year = n;
else
break syntax;
prevc = 0;
} else if (c == '/' || c == ':' || c == '+' || c == '-')
prevc = c;
else {
int st = i - 1;
while (i < limit) {
c = s.charAt(i);
if (!('A' < = c && c < = 'Z' || 'a' < = c && c < = 'z'))
break;
i++;
}
if (i < = st + 1)
break syntax;
int k;
for (k = wtb.length; --k >= 0;)
if (wtb[k].regionMatches(true, 0, s, st, i - st)) {
int action = ttb[k];
if (action != 0) {
if (action == 1) { // pm
if (hour > 12 || hour < 1)
break syntax;
else if (hour < 12)
hour += 12;
} else if (action == 14) { // am
if (hour > 12 || hour < 1)
break syntax;
else if (hour == 12)
hour = 0;
} else if (action < = 13) { // month!
if (mon < 0)
mon = (byte) (action - 2);
else
break syntax;
} else {
tzoffset = action - 10000;
}
}
break;
}
if (k < 0)
break syntax;
prevc = 0;
}
}
if (year == Integer.MIN_VALUE || mon < 0 || mday < 0)
break syntax;
// Parse 2-digit years within the correct default century.
if (year < 100) {
synchronized (Date.class) {
if (defaultCenturyStart == 0) {
defaultCenturyStart = gcal.getCalendarDate().getYear() - 80;
}
}
year += (defaultCenturyStart / 100) * 100;
if (year < defaultCenturyStart) year += 100;
}
if (sec < 0)
sec = 0;
if (min < 0)
min = 0;
if (hour < 0)
hour = 0;
BaseCalendar cal = getCalendarSystem(year);
if (tzoffset == -1) { // no time zone specified, have to use local
BaseCalendar.Date ldate = (BaseCalendar.Date) cal.newCalendarDate(TimeZone.getDefaultRef());
ldate.setDate(year, mon + 1, mday);
ldate.setTimeOfDay(hour, min, sec, 0);
return cal.getTime(ldate);
}
BaseCalendar.Date udate = (BaseCalendar.Date) cal.newCalendarDate(null); // no time zone
udate.setDate(year, mon + 1, mday);
udate.setTimeOfDay(hour, min, sec, 0);
return cal.getTime(udate) + tzoffset * (60 * 1000);
}
// syntax error
throw new IllegalArgumentException();
} Deprecated! As - of JDK version 1.1,
replaced by DateFormat.parse(String s).
Attempts to interpret the string s as a representation
of a date and time. If the attempt is successful, the time
indicated is returned represented as the distance, measured in
milliseconds, of that time from the epoch (00:00:00 GMT on
January 1, 1970). If the attempt fails, an
IllegalArgumentException is thrown.
It accepts many syntaxes; in particular, it recognizes the IETF
standard date syntax: "Sat, 12 Aug 1995 13:30:00 GMT". It also
understands the continental U.S. time-zone abbreviations, but for
general use, a time-zone offset should be used: "Sat, 12 Aug 1995
13:30:00 GMT+0430" (4 hours, 30 minutes west of the Greenwich
meridian). If no time zone is specified, the local time zone is
assumed. GMT and UTC are considered equivalent.
The string s is processed from left to right, looking for
data of interest. Any material in s that is within the
ASCII parenthesis characters ( and ) is ignored.
Parentheses may be nested. Otherwise, the only characters permitted
within s are these ASCII characters:
abcdefghijklmnopqrstuvwxyz
ABCDEFGHIJKLMNOPQRSTUVWXYZ
0123456789,+-:/
and whitespace characters.
A consecutive sequence of decimal digits is treated as a decimal
number:
- If a number is preceded by + or - and a year
has already been recognized, then the number is a time-zone
offset. If the number is less than 24, it is an offset measured
in hours. Otherwise, it is regarded as an offset in minutes,
expressed in 24-hour time format without punctuation. A
preceding - means a westward offset. Time zone offsets
are always relative to UTC (Greenwich). Thus, for example,
-5 occurring in the string would mean "five hours west
of Greenwich" and +0430 would mean "four hours and
thirty minutes east of Greenwich." It is permitted for the
string to specify GMT, UT, or UTC
redundantly-for example, GMT-5 or utc+0430.
- The number is regarded as a year number if one of the
following conditions is true:
- The number is equal to or greater than 70 and followed by a
space, comma, slash, or end of string
- The number is less than 70, and both a month and a day of
the month have already been recognized
If the recognized year number is less than 100, it is
interpreted as an abbreviated year relative to a century of
which dates are within 80 years before and 19 years after
the time when the Date class is initialized.
After adjusting the year number, 1900 is subtracted from
it. For example, if the current year is 1999 then years in
the range 19 to 99 are assumed to mean 1919 to 1999, while
years from 0 to 18 are assumed to mean 2000 to 2018. Note
that this is slightly different from the interpretation of
years less than 100 that is used in java.text.SimpleDateFormat .
- If the number is followed by a colon, it is regarded as an hour,
unless an hour has already been recognized, in which case it is
regarded as a minute.
- If the number is followed by a slash, it is regarded as a month
(it is decreased by 1 to produce a number in the range 0
to 11), unless a month has already been recognized, in
which case it is regarded as a day of the month.
- If the number is followed by whitespace, a comma, a hyphen, or
end of string, then if an hour has been recognized but not a
minute, it is regarded as a minute; otherwise, if a minute has
been recognized but not a second, it is regarded as a second;
otherwise, it is regarded as a day of the month.
A consecutive sequence of letters is regarded as a word and treated
as follows:
- A word that matches AM, ignoring case, is ignored (but
the parse fails if an hour has not been recognized or is less
than 1 or greater than 12).
- A word that matches PM, ignoring case, adds 12
to the hour (but the parse fails if an hour has not been
recognized or is less than 1 or greater than 12).
- Any word that matches any prefix of SUNDAY, MONDAY, TUESDAY,
WEDNESDAY, THURSDAY, FRIDAY, or SATURDAY, ignoring
case, is ignored. For example, sat, Friday, TUE, and
Thurs are ignored.
- Otherwise, any word that matches any prefix of JANUARY,
FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER,
OCTOBER, NOVEMBER, or DECEMBER, ignoring case, and
considering them in the order given here, is recognized as
specifying a month and is converted to a number (0 to
11). For example, aug, Sept, april, and
NOV are recognized as months. So is Ma, which
is recognized as MARCH, not MAY.
- Any word that matches GMT, UT, or UTC, ignoring
case, is treated as referring to UTC.
- Any word that matches EST, CST, MST, or PST,
ignoring case, is recognized as referring to the time zone in
North America that is five, six, seven, or eight hours west of
Greenwich, respectively. Any word that matches EDT, CDT,
MDT, or PDT, ignoring case, is recognized as
referring to the same time zone, respectively, during daylight
saving time.
Once the entire string s has been scanned, it is converted to a time
result in one of two ways. If a time zone or time-zone offset has been
recognized, then the year, month, day of month, hour, minute, and
second are interpreted in UTC and then the time-zone offset is
applied. Otherwise, the year, month, day of month, hour, minute, and
second are interpreted in the local time zone. |
public void setDate(int date) {
getCalendarDate().setDayOfMonth(date);
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.set(Calendar.DAY_OF_MONTH, int date).
Sets the day of the month of this Date object to the
specified value. This Date object is modified so that
it represents a point in time within the specified day of the
month, with the year, month, hour, minute, and second the same
as before, as interpreted in the local time zone. If the date
was April 30, for example, and the date is set to 31, then it
will be treated as if it were on May 1, because April has only
30 days. |
public void setHours(int hours) {
getCalendarDate().setHours(hours);
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.set(Calendar.HOUR_OF_DAY, int hours).
Sets the hour of this Date object to the specified value.
This Date object is modified so that it represents a point
in time within the specified hour of the day, with the year, month,
date, minute, and second the same as before, as interpreted in the
local time zone. |
public void setMinutes(int minutes) {
getCalendarDate().setMinutes(minutes);
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.set(Calendar.MINUTE, int minutes).
Sets the minutes of this Date object to the specified value.
This Date object is modified so that it represents a point
in time within the specified minute of the hour, with the year, month,
date, hour, and second the same as before, as interpreted in the
local time zone. |
public void setMonth(int month) {
int y = 0;
if (month >= 12) {
y = month / 12;
month %= 12;
} else if (month < 0) {
y = CalendarUtils.floorDivide(month, 12);
month = CalendarUtils.mod(month, 12);
}
BaseCalendar.Date d = getCalendarDate();
if (y != 0) {
d.setNormalizedYear(d.getNormalizedYear() + y);
}
d.setMonth(month + 1); // adjust 0-based to 1-based month numbering
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.set(Calendar.MONTH, int month).
Sets the month of this date to the specified value. This
Date object is modified so that it represents a point
in time within the specified month, with the year, date, hour,
minute, and second the same as before, as interpreted in the
local time zone. If the date was October 31, for example, and
the month is set to June, then the new date will be treated as
if it were on July 1, because June has only 30 days. |
public void setSeconds(int seconds) {
getCalendarDate().setSeconds(seconds);
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.set(Calendar.SECOND, int seconds).
Sets the seconds of this Date to the specified value.
This Date object is modified so that it represents a
point in time within the specified second of the minute, with
the year, month, date, hour, and minute the same as before, as
interpreted in the local time zone. |
public void setTime(long time) {
fastTime = time;
cdate = null;
} Sets this Date object to represent a point in time that is
time milliseconds after January 1, 1970 00:00:00 GMT. |
public void setYear(int year) {
getCalendarDate().setNormalizedYear(year + 1900);
} Deprecated! As - of JDK version 1.1,
replaced by Calendar.set(Calendar.YEAR, year + 1900).
Sets the year of this Date object to be the specified
value plus 1900. This Date object is modified so
that it represents a point in time within the specified year,
with the month, date, hour, minute, and second the same as
before, as interpreted in the local time zone. (Of course, if
the date was February 29, for example, and the year is set to a
non-leap year, then the new date will be treated as if it were
on March 1.) |
public String toGMTString() {
// d MMM yyyy HH:mm:ss 'GMT'
long t = getTime();
BaseCalendar cal = getCalendarSystem(t);
BaseCalendar.Date date =
(BaseCalendar.Date) cal.getCalendarDate(getTime(), (TimeZone)null);
StringBuilder sb = new StringBuilder(32);
CalendarUtils.sprintf0d(sb, date.getDayOfMonth(), 1).append(' '); // d
convertToAbbr(sb, wtb[date.getMonth() - 1 + 2 + 7]).append(' '); // MMM
sb.append(date.getYear()).append(' '); // yyyy
CalendarUtils.sprintf0d(sb, date.getHours(), 2).append(':'); // HH
CalendarUtils.sprintf0d(sb, date.getMinutes(), 2).append(':'); // mm
CalendarUtils.sprintf0d(sb, date.getSeconds(), 2); // ss
sb.append(" GMT"); // ' GMT'
return sb.toString();
} Deprecated! As - of JDK version 1.1,
replaced by DateFormat.format(Date date), using a
GMT TimeZone.
|
public String toLocaleString() {
DateFormat formatter = DateFormat.getDateTimeInstance();
return formatter.format(this);
} Deprecated! As - of JDK version 1.1,
replaced by DateFormat.format(Date date).
Creates a string representation of this Date object in an
implementation-dependent form. The intent is that the form should
be familiar to the user of the Java application, wherever it may
happen to be running. The intent is comparable to that of the
"%c" format supported by the strftime()
function of ISO C. |
public String toString() {
// "EEE MMM dd HH:mm:ss zzz yyyy";
BaseCalendar.Date date = normalize();
StringBuilder sb = new StringBuilder(28);
int index = date.getDayOfWeek();
if (index == gcal.SUNDAY) {
index = 8;
}
convertToAbbr(sb, wtb[index]).append(' '); // EEE
convertToAbbr(sb, wtb[date.getMonth() - 1 + 2 + 7]).append(' '); // MMM
CalendarUtils.sprintf0d(sb, date.getDayOfMonth(), 2).append(' '); // dd
CalendarUtils.sprintf0d(sb, date.getHours(), 2).append(':'); // HH
CalendarUtils.sprintf0d(sb, date.getMinutes(), 2).append(':'); // mm
CalendarUtils.sprintf0d(sb, date.getSeconds(), 2).append(' '); // ss
TimeZone zi = date.getZone();
if (zi != null) {
sb.append(zi.getDisplayName(date.isDaylightTime(), zi.SHORT, Locale.US)); // zzz
} else {
sb.append("GMT");
}
sb.append(' ').append(date.getYear()); // yyyy
return sb.toString();
} |
java.util.Date