Class UniversalTimeScale
- java.lang.Object
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- com.ibm.icu.util.UniversalTimeScale
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public final class UniversalTimeScale extends java.lang.Object
There are quite a few different conventions for binary datetime, depending on different platforms and protocols. Some of these have severe drawbacks. For example, people using Unix time (seconds since Jan 1, 1970, usually in a 32-bit integer) think that they are safe until near the year 2038. But cases can and do arise where arithmetic manipulations causes serious problems. Consider the computation of the average of two datetimes, for example: if one calculates them withaverageTime = (time1 + time2)/2
, there will be overflow even with dates beginning in 2004. Moreover, even if these problems don't occur, there is the issue of conversion back and forth between different systems.Binary datetimes differ in a number of ways: the datatype, the unit, and the epoch (origin). We refer to these as time scales.
ICU implements a universal time scale that is similar to the .NET framework's System.DateTime. The universal time scale is a 64-bit integer that holds ticks since midnight, January 1st, 0001. (One tick is 100 nanoseconds.) Negative values are supported. This has enough range to guarantee that calculations involving dates around the present are safe.
The universal time scale always measures time according to the proleptic Gregorian calendar. That is, the Gregorian calendar's leap year rules are used for all times, even before 1582 when it was introduced. (This is different from the default ICU calendar which switches from the Julian to the Gregorian calendar in 1582. See GregorianCalendar.setGregorianChange() and ucal_setGregorianChange().) ICU provides conversion functions to and from all other major time scales, allowing datetimes in any time scale to be converted to the universal time scale, safely manipulated, and converted back to any other datetime time scale.
For more details and background, see the Universal Time Scale chapter in the ICU User Guide.
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Nested Class Summary
Nested Classes Modifier and Type Class Description private static class
UniversalTimeScale.TimeScaleData
This class holds the data that describes a particular time scale.
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Field Summary
Fields Modifier and Type Field Description private static long
days
static int
DB2_TIME
Used in DB2.static int
DOTNET_DATE_TIME
Used in the .NET framework'sSystem.DateTime
structure.static int
EPOCH_OFFSET_MINUS_1_VALUE
Deprecated.This API is ICU internal only.static int
EPOCH_OFFSET_PLUS_1_VALUE
The constant used to select the epoch plus one value for a time scale.static int
EPOCH_OFFSET_VALUE
The constant used to select the epoch offset value for a time scale.static int
EXCEL_TIME
Used in Excel.static int
FROM_MAX_VALUE
The constant used to select the maximum from value for a time scale.static int
FROM_MIN_VALUE
The constant used to select the minimum from value for a time scale.private static long
hours
static int
ICU4C_TIME
Used in the ICU4C.static int
JAVA_TIME
Used in the JDK.static int
MAC_OLD_TIME
Used in older Macintosh systems.static int
MAC_TIME
Used in the JDK.static int
MAX_ROUND_VALUE
Deprecated.This API is ICU internal only.static int
MAX_SCALE
Deprecated.ICU 59static int
MAX_SCALE_VALUE
Deprecated.This API is ICU internal only.private static long
microseconds
private static long
milliseconds
static int
MIN_ROUND_VALUE
Deprecated.This API is ICU internal only.private static long
minutes
private static long
seconds
private static long
ticks
private static UniversalTimeScale.TimeScaleData[]
timeScaleTable
static int
TO_MAX_VALUE
The constant used to select the maximum to value for a time scale.static int
TO_MIN_VALUE
The constant used to select the minimum to value for a time scale.static int
UNITS_ROUND_VALUE
Deprecated.This API is ICU internal only.static int
UNITS_VALUE
The constant used to select the units value for a time scale.static int
UNIX_MICROSECONDS_TIME
Data is along
.static int
UNIX_TIME
Used in Unix systems.static int
WINDOWS_FILE_TIME
Used in Windows for file times.
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Constructor Summary
Constructors Modifier Constructor Description private
UniversalTimeScale()
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Method Summary
All Methods Static Methods Concrete Methods Deprecated Methods Modifier and Type Method Description static BigDecimal
bigDecimalFrom(double otherTime, int timeScale)
Convert adouble
datetime from the given time scale to the universal time scale.static BigDecimal
bigDecimalFrom(long otherTime, int timeScale)
Convert along
datetime from the given time scale to the universal time scale.static BigDecimal
bigDecimalFrom(BigDecimal otherTime, int timeScale)
Convert aBigDecimal
datetime from the given time scale to the universal time scale.static long
from(long otherTime, int timeScale)
Convert along
datetime from the given time scale to the universal time scale.private static UniversalTimeScale.TimeScaleData
fromRangeCheck(long otherTime, int scale)
private static UniversalTimeScale.TimeScaleData
getTimeScaleData(int scale)
Return theTimeScaleData
object for the given time scale.static long
getTimeScaleValue(int scale, int value)
Get a value associated with a particular time scale.static BigDecimal
toBigDecimal(long universalTime, int timeScale)
Convert a datetime from the universal time scale to aBigDecimal
in the given time scale.static BigDecimal
toBigDecimal(BigDecimal universalTime, int timeScale)
Convert a datetime from the universal time scale to aBigDecimal
in the given time scale.static BigDecimal
toBigDecimalTrunc(BigDecimal universalTime, int timeScale)
Deprecated.This API is ICU internal only.static long
toLong(long universalTime, int timeScale)
Convert a datetime from the universal time scale stored as aBigDecimal
to along
in the given time scale.private static UniversalTimeScale.TimeScaleData
toRangeCheck(long universalTime, int scale)
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Field Detail
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JAVA_TIME
public static final int JAVA_TIME
Used in the JDK. Data is along
. Value is milliseconds since January 1, 1970.- See Also:
- Constant Field Values
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UNIX_TIME
public static final int UNIX_TIME
Used in Unix systems. Data is anint
or along
. Value is seconds since January 1, 1970.- See Also:
- Constant Field Values
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ICU4C_TIME
public static final int ICU4C_TIME
Used in the ICU4C. Data is adouble
. Value is milliseconds since January 1, 1970.- See Also:
- Constant Field Values
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WINDOWS_FILE_TIME
public static final int WINDOWS_FILE_TIME
Used in Windows for file times. Data is along
. Value is ticks (1 tick == 100 nanoseconds) since January 1, 1601.- See Also:
- Constant Field Values
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DOTNET_DATE_TIME
public static final int DOTNET_DATE_TIME
Used in the .NET framework'sSystem.DateTime
structure. Data is along
. Value is ticks (1 tick == 100 nanoseconds) since January 1, 0001.- See Also:
- Constant Field Values
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MAC_OLD_TIME
public static final int MAC_OLD_TIME
Used in older Macintosh systems. Data is anint
. Value is seconds since January 1, 1904.- See Also:
- Constant Field Values
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MAC_TIME
public static final int MAC_TIME
Used in the JDK. Data is adouble
. Value is milliseconds since January 1, 2001.- See Also:
- Constant Field Values
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EXCEL_TIME
public static final int EXCEL_TIME
Used in Excel. Data is a?unknown?
. Value is days since December 31, 1899.- See Also:
- Constant Field Values
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DB2_TIME
public static final int DB2_TIME
Used in DB2. Data is a?unknown?
. Value is days since December 31, 1899.- See Also:
- Constant Field Values
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UNIX_MICROSECONDS_TIME
public static final int UNIX_MICROSECONDS_TIME
Data is along
. Value is microseconds since January 1, 1970. Similar to Unix time (linear value from 1970) and struct timeval (microseconds resolution).- See Also:
- Constant Field Values
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MAX_SCALE
@Deprecated public static final int MAX_SCALE
Deprecated.ICU 59This is the first unused time scale value.- See Also:
- Constant Field Values
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UNITS_VALUE
public static final int UNITS_VALUE
The constant used to select the units value for a time scale.- See Also:
- Constant Field Values
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EPOCH_OFFSET_VALUE
public static final int EPOCH_OFFSET_VALUE
The constant used to select the epoch offset value for a time scale.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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FROM_MIN_VALUE
public static final int FROM_MIN_VALUE
The constant used to select the minimum from value for a time scale.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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FROM_MAX_VALUE
public static final int FROM_MAX_VALUE
The constant used to select the maximum from value for a time scale.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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TO_MIN_VALUE
public static final int TO_MIN_VALUE
The constant used to select the minimum to value for a time scale.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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TO_MAX_VALUE
public static final int TO_MAX_VALUE
The constant used to select the maximum to value for a time scale.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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EPOCH_OFFSET_PLUS_1_VALUE
public static final int EPOCH_OFFSET_PLUS_1_VALUE
The constant used to select the epoch plus one value for a time scale. NOTE: This is an internal value. DO NOT USE IT. May not actually be equal to the epoch offset value plus one.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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EPOCH_OFFSET_MINUS_1_VALUE
@Deprecated public static final int EPOCH_OFFSET_MINUS_1_VALUE
Deprecated.This API is ICU internal only.The constant used to select the epoch offset minus one value for a time scale. NOTE: This is an internal value. DO NOT USE IT. May not actually be equal to the epoch offset value minus one.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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UNITS_ROUND_VALUE
@Deprecated public static final int UNITS_ROUND_VALUE
Deprecated.This API is ICU internal only.The constant used to select the units round value for a time scale. NOTE: This is an internal value. DO NOT USE IT.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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MIN_ROUND_VALUE
@Deprecated public static final int MIN_ROUND_VALUE
Deprecated.This API is ICU internal only.The constant used to select the minimum safe rounding value for a time scale. NOTE: This is an internal value. DO NOT USE IT.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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MAX_ROUND_VALUE
@Deprecated public static final int MAX_ROUND_VALUE
Deprecated.This API is ICU internal only.The constant used to select the maximum safe rounding value for a time scale. NOTE: This is an internal value. DO NOT USE IT.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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MAX_SCALE_VALUE
@Deprecated public static final int MAX_SCALE_VALUE
Deprecated.This API is ICU internal only.The number of time scale values. NOTE: This is an internal value. DO NOT USE IT.- See Also:
getTimeScaleValue(int, int)
, Constant Field Values
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ticks
private static final long ticks
- See Also:
- Constant Field Values
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microseconds
private static final long microseconds
- See Also:
- Constant Field Values
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milliseconds
private static final long milliseconds
- See Also:
- Constant Field Values
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seconds
private static final long seconds
- See Also:
- Constant Field Values
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minutes
private static final long minutes
- See Also:
- Constant Field Values
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hours
private static final long hours
- See Also:
- Constant Field Values
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days
private static final long days
- See Also:
- Constant Field Values
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timeScaleTable
private static final UniversalTimeScale.TimeScaleData[] timeScaleTable
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Method Detail
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from
public static long from(long otherTime, int timeScale)
Convert along
datetime from the given time scale to the universal time scale.- Parameters:
otherTime
- Thelong
datetimetimeScale
- The time scale to convert from- Returns:
- The datetime converted to the universal time scale
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bigDecimalFrom
public static BigDecimal bigDecimalFrom(double otherTime, int timeScale)
Convert adouble
datetime from the given time scale to the universal time scale. All calculations are done usingBigDecimal
to guarantee that the value does not go out of range.- Parameters:
otherTime
- Thedouble
datetimetimeScale
- The time scale to convert from- Returns:
- The datetime converted to the universal time scale
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bigDecimalFrom
public static BigDecimal bigDecimalFrom(long otherTime, int timeScale)
Convert along
datetime from the given time scale to the universal time scale. All calculations are done usingBigDecimal
to guarantee that the value does not go out of range.- Parameters:
otherTime
- Thelong
datetimetimeScale
- The time scale to convert from- Returns:
- The datetime converted to the universal time scale
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bigDecimalFrom
public static BigDecimal bigDecimalFrom(BigDecimal otherTime, int timeScale)
Convert aBigDecimal
datetime from the given time scale to the universal time scale. All calculations are done usingBigDecimal
to guarantee that the value does not go out of range.- Parameters:
otherTime
- TheBigDecimal
datetimetimeScale
- The time scale to convert from- Returns:
- The datetime converted to the universal time scale
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toLong
public static long toLong(long universalTime, int timeScale)
Convert a datetime from the universal time scale stored as aBigDecimal
to along
in the given time scale. Since this calculation requires a divide, we must round. The straight forward way to round by adding half of the divisor will push the sum out of range for values within have the divisor of the limits of the precision of along
. To get around this, we do the rounding like this:(universalTime - units + units/2) / units + 1
(i.e. we subtract units first to guarantee that we'll still be in range when we add
units/2
. We then need to add one to the quotent to make up for the extra subtraction. This simplifies to:(universalTime - units/2) / units - 1
For negative values to round away from zero, we need to flip the signs:
(universalTime + units/2) / units + 1
Since we also need to subtract the epochOffset, we fold the
+/- 1
into the offset value. (i.e.epochOffsetP1
,epochOffsetM1
.)- Parameters:
universalTime
- The datetime in the universal time scaletimeScale
- The time scale to convert to- Returns:
- The datetime converted to the given time scale
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toBigDecimal
public static BigDecimal toBigDecimal(long universalTime, int timeScale)
Convert a datetime from the universal time scale to aBigDecimal
in the given time scale.- Parameters:
universalTime
- The datetime in the universal time scaletimeScale
- The time scale to convert to- Returns:
- The datetime converted to the given time scale
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toBigDecimal
public static BigDecimal toBigDecimal(BigDecimal universalTime, int timeScale)
Convert a datetime from the universal time scale to aBigDecimal
in the given time scale.- Parameters:
universalTime
- The datetime in the universal time scaletimeScale
- The time scale to convert to- Returns:
- The datetime converted to the given time scale
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getTimeScaleData
private static UniversalTimeScale.TimeScaleData getTimeScaleData(int scale)
Return theTimeScaleData
object for the given time scale.- Parameters:
scale
- - the time scale- Returns:
- the
TimeScaleData
object for the given time scale
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getTimeScaleValue
public static long getTimeScaleValue(int scale, int value)
Get a value associated with a particular time scale.- Parameters:
scale
- - the time scalevalue
- - a constant representing the value to get- Returns:
- - the value.
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toRangeCheck
private static UniversalTimeScale.TimeScaleData toRangeCheck(long universalTime, int scale)
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fromRangeCheck
private static UniversalTimeScale.TimeScaleData fromRangeCheck(long otherTime, int scale)
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toBigDecimalTrunc
@Deprecated public static BigDecimal toBigDecimalTrunc(BigDecimal universalTime, int timeScale)
Deprecated.This API is ICU internal only.Convert a time in the Universal Time Scale into another time scale. The division used to do the conversion rounds down. NOTE: This is an internal routine used by the tool that generates the to and from limits. Use it at your own risk.- Parameters:
universalTime
- the time in the Universal Time scaletimeScale
- the time scale to convert to- Returns:
- the time in the given time scale
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