public final class UTCInstant extends Object implements Comparable<UTCInstant>, Serializable
Most of the Time Framework for Java works on the assumption that the time-line is simple, there are no leap-seconds and there are always 24 * 60 * 60 seconds in a day. However, the Earth's rotation is not straightforward, and a solar day does not match this definition.
This class is an alternative representation based on the UTC time-scale which
includes leap-seconds. Leap-seconds are additional seconds that are inserted into the
year-month-day-hour-minute-second time-line in order to keep UTC in line with the solar day.
When a leap second occurs, an accurate clock will show the time 23:59:60
just before midnight.
Leap-seconds are announced in advance, typically at least six months.
The UTCRules
class models which dates have leap-seconds.
Alternative implementations of the rules may be supplied.
The default rules implementation fixes the start point of UTC as 1972. This date was chosen as UTC was more complex before 1972.
The duration between two points on the UTC time-scale is calculated solely using this class.
Do not use the between
method on Duration
as that will lose information.
Instead use durationUntil(UTCInstant)
on this class.
It is intended that most applications will use the Instant
class
which uses the UTC-SLS mapping from UTC to guarantee 86400 seconds per day.
Specialist applications with access to an accurate time-source may find this class useful.
The length of the solar day is the standard way that humans measure time. As the Earth's rotation changes, the length of the day varies. In general, a solar day is slightly longer than 86400 seconds. The actual length is not predictable and can only be determined by measurement. The UT1 time-scale captures these measurements.
The UTC time-scale is a standard approach to bundle up all the additional fractions
of a second from UT1 into whole seconds, known as leap-seconds.
A leap-second may be added or removed depending on the Earth's rotational changes.
If it is removed, then the relevant date will have no time of 23:59:59
.
If it is added, then the relevant date will have an extra second of 23:59:60
.
The modern UTC time-scale was introduced in 1972, introducing the concept of whole leap-seconds. Between 1958 and 1972, the definition of UTC was complex, with minor sub-second leaps and alterations to the length of seconds. The default rules only implement UTC from 1972. Prior to that date, the default rules fix the UTC-TAI offset at 10 seconds. While not historically accurate, it is a simple, easy definition, suitable for this library.
The standard Java epoch of 1970-01-01
is prior to the introduction of whole leap-seconds into UTC in 1972.
As such, the Time Framework for Java needs to define what the 1970 epoch actually means.
The chosen definition follows the UTC definition given above, such that 1970-01-01
is 10 seconds
offset from TAI.
UTCInstant is immutable and thread-safe.
Modifier and Type | Method and Description |
---|---|
int |
compareTo(UTCInstant otherInstant)
Compares this instant to another based on the time-line, then the name
of the rules.
|
Duration |
durationUntil(UTCInstant utcInstant)
Returns the duration between this instant and the specified instant.
|
boolean |
equals(Object otherInstant)
Checks if this instant is equal to the specified
UTCInstant . |
long |
getModifiedJulianDays()
Gets the Modified Julian Day (MJD).
|
long |
getNanoOfDay()
Gets the number of nanoseconds, later along the time-line, from the start
of the Modified Julian Day.
|
UTCRules |
getRules()
Gets the leap second rules defining when leap seconds occur.
|
int |
hashCode()
Returns a hash code for this instant.
|
boolean |
isLeapSecond()
Checks if the instant is within a leap second.
|
UTCInstant |
minus(Duration duration)
Returns a copy of this instant with the specified duration subtracted.
|
static UTCInstant |
of(Instant instant)
Obtains an instance of
UTCInstant from a provider of instants
using the system default leap second rules. |
static UTCInstant |
of(Instant instant,
UTCRules rules)
Obtains an instance of
UTCInstant from a provider of instants
using the specified leap second rules. |
static UTCInstant |
of(TAIInstant taiInstant)
Obtains an instance of
UTCInstant from a TAI instant
using the system default leap second rules. |
static UTCInstant |
of(TAIInstant taiInstant,
UTCRules rules)
Obtains an instance of
UTCInstant from a TAI instant
using the specified leap second rules. |
static UTCInstant |
ofModifiedJulianDays(long mjDay,
long nanoOfDay)
Obtains an instance of
UTCInstant from a Modified Julian Day with
a nanosecond fraction of second using the system default leap second rules. |
static UTCInstant |
ofModifiedJulianDays(long mjDay,
long nanoOfDay,
UTCRules rules)
Obtains an instance of
UTCInstant from a Modified Julian Day with
a nanosecond fraction of second using the specified leap second rules. |
UTCInstant |
plus(Duration duration)
Returns a copy of this instant with the specified duration added.
|
Instant |
toInstant()
Converts this instant to an
Instant using the system default
leap second rules. |
String |
toString()
A string representation of this instant.
|
TAIInstant |
toTAIInstant()
Converts this instant to a
TAIInstant using the stored
leap second rules. |
public static UTCInstant ofModifiedJulianDays(long mjDay, long nanoOfDay)
UTCInstant
from a Modified Julian Day with
a nanosecond fraction of second using the system default leap second rules.
This factory creates an instance of a UTC instant.
The nanosecond of day value includes any leap second and has a valid range from
0
to 86,400,000,000,000 - 1
on days other than leap-second-days
and other lengths on leap-second-days.
The nanosecond value must be positive even for negative values of Modified
Julian Days. One nanosecond before Modified Julian Day zero will be
-1
days and the maximum nanosecond value.
mjDay
- the date as a Modified Julian Day (number of days from the epoch of 1858-11-17)nanoOfDay
- the nanoseconds within the day, including leap secondsIllegalArgumentException
- if nanoOfDay is out of rangepublic static UTCInstant ofModifiedJulianDays(long mjDay, long nanoOfDay, UTCRules rules)
UTCInstant
from a Modified Julian Day with
a nanosecond fraction of second using the specified leap second rules.
This factory creates an instance of a UTC instant.
The nanosecond of day value includes any leap second and has a valid range from
0
to 86,400,000,000,000 - 1
on days other than leap-second-days
and other lengths on leap-second-days.
The nanosecond value must be positive even for negative values of Modified
Julian Days. One nanosecond before Modified Julian Day zero will be
-1
days and the maximum nanosecond value.
mjDay
- the date as a Modified Julian Day (number of days from the epoch of 1858-11-17)nanoOfDay
- the nanoseconds within the day, including leap secondsIllegalArgumentException
- if nanoOfDay is out of rangepublic static UTCInstant of(Instant instant)
UTCInstant
from a provider of instants
using the system default leap second rules.
This method converts from the UTC-SLS to the UTC time-scale using the
system default leap-second rules. This conversion will lose information
around a leap second in accordance with UTC-SLS.
Converting back to an Instant
may result in a slightly different instant.
instant
- the instant to convert, not nullpublic static UTCInstant of(Instant instant, UTCRules rules)
UTCInstant
from a provider of instants
using the specified leap second rules.
This method converts from the UTC-SLS to the UTC time-scale using the
specified leap-second rules. This conversion will lose information
around a leap second in accordance with UTC-SLS.
Converting back to an Instant
may result in a slightly different instant.
instant
- the instant to convert, not nullrules
- the leap second rules, not nullpublic static UTCInstant of(TAIInstant taiInstant)
UTCInstant
from a TAI instant
using the system default leap second rules.
This method converts from the TAI to the UTC time-scale using the
system default leap-second rules. This conversion does not lose information
and the UTC instant may safely be converted back to a TAIInstant
.
taiInstant
- the TAI instant to convert, not nullpublic static UTCInstant of(TAIInstant taiInstant, UTCRules rules)
UTCInstant
from a TAI instant
using the specified leap second rules.
This method converts from the TAI to the UTC time-scale using the
specified leap-second rules. This conversion does not lose information
and the UTC instant may safely be converted back to a TAIInstant
.
taiInstant
- the TAI instant to convert, not nullrules
- the leap second rules, not nullpublic UTCRules getRules()
public long getModifiedJulianDays()
The Modified Julian Day count is a simple incrementing count of days
where day 0 is 1858-11-17.
The nanosecond part of the day is returned by getNanosOfDay
.
A Modified Julian Day varies in length, being one second longer on a leap day.
public long getNanoOfDay()
The nanosecond-of-day value measures the total number of nanoseconds from
the Modified Julian Day returned by getModifiedJulianDay
.
This value will include any additional leap seconds.
public boolean isLeapSecond()
This method returns true when an accurate clock would return a seconds field of 60.
public UTCInstant plus(Duration duration)
The duration is added using simple addition of the seconds and nanoseconds in the duration to the seconds and nanoseconds of this instant. As a result, the duration is treated as being measured in TAI compatible seconds for the purpose of this method.
This instance is immutable and unaffected by this method call.
duration
- the duration to add, not nullUTCInstant
with the duration added, never nullArithmeticException
- if the calculation exceeds the supported rangepublic UTCInstant minus(Duration duration)
The duration is subtracted using simple subtraction of the seconds and nanoseconds in the duration from the seconds and nanoseconds of this instant. As a result, the duration is treated as being measured in TAI compatible seconds for the purpose of this method.
This instance is immutable and unaffected by this method call.
duration
- the duration to subtract, not nullUTCInstant
with the duration subtracted, never nullArithmeticException
- if the calculation exceeds the supported rangepublic Duration durationUntil(UTCInstant utcInstant)
This calculates the duration between this instant and another based on
the UTC time-scale. Any leap seconds that occur will be included in the duration.
Adding the duration to this instant using plus(javax.time.Duration)
will always result
in an instant equal to the specified instant.
utcInstant
- the instant to calculate the duration until, not nullArithmeticException
- if the calculation exceeds the supported rangepublic TAIInstant toTAIInstant()
TAIInstant
using the stored
leap second rules.
This method converts from the UTC to the TAI time-scale using the stored leap-second rules.
Conversion to a TAIInstant
retains the same point on the time-line
but loses the stored rules. If the TAI instant is converted back to a UTC instant
with different or updated rules then the calculated UTC instant may be different.
TAIInstant
representing the same instant, never nullArithmeticException
- if the calculation exceeds the supported rangepublic Instant toInstant()
Instant
using the system default
leap second rules.
This method converts this instant from the UTC to the UTC-SLS time-scale using the
stored leap-second rules.
This conversion will lose information around a leap second in accordance with UTC-SLS.
Converting back to a UTCInstant
may result in a slightly different instant.
Instant
representing the best approximation of this instant, never nullArithmeticException
- if the calculation exceeds the supported rangepublic int compareTo(UTCInstant otherInstant)
The comparison is based on the positions on the time-line and the rules.
This definition means that two instants representing the same instant on
the time-line will differ if the rules differ. To compare the time-line
instant, convert both instants to a TAIInstant
.
compareTo
in interface Comparable<UTCInstant>
otherInstant
- the other instant to compare to, not nullpublic boolean equals(Object otherInstant)
UTCInstant
.
The comparison is based on the positions on the time-line and the rules.
This definition means that two instants representing the same instant on
the time-line will differ if the rules differ. To compare the time-line
instant, convert both instants to a TAIInstant
.
public int hashCode()
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