UniversalTimeScale

java.lang.Object
- ohos.global.icu.util.UniversalTimeScale

```
public final class UniversalTimeScale
extends 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 with averageTime = (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.

字段概要

字段
限定符和类型	字段	说明
`static int`	`DB2_TIME`	Used in DB2.
`static int`	`DOTNET_DATE_TIME`	Used in the .NET framework's `System.DateTime` structure.
`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.
`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_SCALE`	已过时。 ICU 59
`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_VALUE`	The constant used to select the units value for a time scale.
`static int`	`UNIX_MICROSECONDS_TIME`	Data is a `long`.
`static int`	`UNIX_TIME`	Used in Unix systems.
`static int`	`WINDOWS_FILE_TIME`	Used in Windows for file times.

方法概要

所有方法静态方法具体方法
限定符和类型	方法	说明
`static BigDecimal`	`bigDecimalFrom(double otherTime, int timeScale)`	Convert a `double` datetime from the given time scale to the universal time scale.
`static BigDecimal`	`bigDecimalFrom(long otherTime, int timeScale)`	Convert a `long` datetime from the given time scale to the universal time scale.
`static BigDecimal`	`bigDecimalFrom(BigDecimal otherTime, int timeScale)`	Convert a `BigDecimal` datetime from the given time scale to the universal time scale.
`static long`	`from(long otherTime, int timeScale)`	Convert a `long` datetime from the given time scale to the universal 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 a `BigDecimal` in the given time scale.
`static BigDecimal`	`toBigDecimal(BigDecimal universalTime, int timeScale)`	Convert a datetime from the universal time scale to a `BigDecimal` in the given time scale.
`static long`	`toLong(long universalTime, int timeScale)`	Convert a datetime from the universal time scale stored as a `BigDecimal` to a `long` in the given time scale.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 字段详细资料
  - DB2_TIME
```
public static final int DB2_TIME
```
    Used in DB2. Data is a ?unknown?. Value is days since December 31, 1899.
    
    另请参阅:
    
    常量字段值
  - DOTNET_DATE_TIME
```
public static final int DOTNET_DATE_TIME
```
    Used in the .NET framework's System.DateTime structure. Data is a long. Value is ticks (1 tick == 100 nanoseconds) since January 1, 0001.
    
    另请参阅:
    
    常量字段值
  - 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.
    
    另请参阅:
    
    getTimeScaleValue(int, int), 常量字段值
  - EPOCH_OFFSET_VALUE
```
public static final int EPOCH_OFFSET_VALUE
```
    The constant used to select the epoch offset value for a time scale.
    
    另请参阅:
    
    getTimeScaleValue(int, int), 常量字段值
  - EXCEL_TIME
```
public static final int EXCEL_TIME
```
    Used in Excel. Data is a ?unknown?. Value is days since December 31, 1899.
    
    另请参阅:
    
    常量字段值
  - FROM_MAX_VALUE
```
public static final int FROM_MAX_VALUE
```
    The constant used to select the maximum from value for a time scale.
    
    另请参阅:
    
    getTimeScaleValue(int, int), 常量字段值
  - FROM_MIN_VALUE
```
public static final int FROM_MIN_VALUE
```
    The constant used to select the minimum from value for a time scale.
    
    另请参阅:
    
    getTimeScaleValue(int, int), 常量字段值
  - ICU4C_TIME
```
public static final int ICU4C_TIME
```
    Used in the ICU4C. Data is a double. Value is milliseconds since January 1, 1970.
    
    另请参阅:
    
    常量字段值
  - JAVA_TIME
```
public static final int JAVA_TIME
```
    Used in the JDK. Data is a long. Value is milliseconds since January 1, 1970.
    
    另请参阅:
    
    常量字段值
  - MAC_OLD_TIME
```
public static final int MAC_OLD_TIME
```
    Used in older Macintosh systems. Data is an int. Value is seconds since January 1, 1904.
    
    另请参阅:
    
    常量字段值
  - MAC_TIME
```
public static final int MAC_TIME
```
    Used in the JDK. Data is a double. Value is milliseconds since January 1, 2001.
    
    另请参阅:
    
    常量字段值
  - MAX_SCALE
```
@Deprecated
public static final int MAX_SCALE
```
    已过时。 ICU 59
    
    This is the first unused time scale value.
    
    另请参阅:
    
    常量字段值
  - TO_MAX_VALUE
```
public static final int TO_MAX_VALUE
```
    The constant used to select the maximum to value for a time scale.
    
    另请参阅:
    
    getTimeScaleValue(int, int), 常量字段值
  - TO_MIN_VALUE
```
public static final int TO_MIN_VALUE
```
    The constant used to select the minimum to value for a time scale.
    
    另请参阅:
    
    getTimeScaleValue(int, int), 常量字段值
  - UNITS_VALUE
```
public static final int UNITS_VALUE
```
    The constant used to select the units value for a time scale.
    
    另请参阅:
    
    常量字段值
  - UNIX_MICROSECONDS_TIME
```
public static final int UNIX_MICROSECONDS_TIME
```
    Data is a long. Value is microseconds since January 1, 1970. Similar to Unix time (linear value from 1970) and struct timeval (microseconds resolution).
    
    另请参阅:
    
    常量字段值
  - UNIX_TIME
```
public static final int UNIX_TIME
```
    Used in Unix systems. Data is an int or a long. Value is seconds since January 1, 1970.
    
    另请参阅:
    
    常量字段值
  - WINDOWS_FILE_TIME
```
public static final int WINDOWS_FILE_TIME
```
    Used in Windows for file times. Data is a long. Value is ticks (1 tick == 100 nanoseconds) since January 1, 1601.
    
    另请参阅:
    
    常量字段值
- 方法详细资料
  - from
```
public static long from(long otherTime,
                        int timeScale)
```
    Convert a long datetime from the given time scale to the universal time scale.
    
    参数:
    
    otherTime - The long datetime
    
    timeScale - The time scale to convert from
    
    返回:
    
    The datetime converted to the universal time scale
  - bigDecimalFrom
```
public static BigDecimal bigDecimalFrom(double otherTime,
                                        int timeScale)
```
    Convert a double datetime from the given time scale to the universal time scale. All calculations are done using BigDecimal to guarantee that the value does not go out of range.
    
    参数:
    
    otherTime - The double datetime
    
    timeScale - The time scale to convert from
    
    返回:
    
    The datetime converted to the universal time scale
  - bigDecimalFrom
```
public static BigDecimal bigDecimalFrom(long otherTime,
                                        int timeScale)
```
    Convert a long datetime from the given time scale to the universal time scale. All calculations are done using BigDecimal to guarantee that the value does not go out of range.
    
    参数:
    
    otherTime - The long datetime
    
    timeScale - The time scale to convert from
    
    返回:
    
    The datetime converted to the universal time scale
  - bigDecimalFrom
```
public static BigDecimal bigDecimalFrom(BigDecimal otherTime,
                                        int timeScale)
```
    Convert a BigDecimal datetime from the given time scale to the universal time scale. All calculations are done using BigDecimal to guarantee that the value does not go out of range.
    
    参数:
    
    otherTime - The BigDecimal datetime
    
    timeScale - The time scale to convert from
    
    返回:
    
    The datetime converted to the universal time scale
  - toLong
```
public static long toLong(long universalTime,
                          int timeScale)
```
    Convert a datetime from the universal time scale stored as a BigDecimal to a long 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 a long. 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.)
    
    参数:
    
    universalTime - The datetime in the universal time scale
    
    timeScale - The time scale to convert to
    
    返回:
    
    The datetime converted to the given time scale
  - toBigDecimal
```
public static BigDecimal toBigDecimal(long universalTime,
                                      int timeScale)
```
    Convert a datetime from the universal time scale to a BigDecimal in the given time scale.
    
    参数:
    
    universalTime - The datetime in the universal time scale
    
    timeScale - The time scale to convert to
    
    返回:
    
    The datetime converted to the given time scale
  - toBigDecimal
```
public static BigDecimal toBigDecimal(BigDecimal universalTime,
                                      int timeScale)
```
    Convert a datetime from the universal time scale to a BigDecimal in the given time scale.
    
    参数:
    
    universalTime - The datetime in the universal time scale
    
    timeScale - The time scale to convert to
    
    返回:
    
    The datetime converted to the given time scale
  - getTimeScaleValue
```
public static long getTimeScaleValue(int scale,
                                     int value)
```
    Get a value associated with a particular time scale.
    
    参数:
    
    scale - - the time scale
    
    value - - a constant representing the value to get
    
    返回:
    
    - the value.

类 UniversalTimeScale

字段概要

方法概要

从类继承的方法 java.lang.Object

字段详细资料

DB2_TIME

DOTNET_DATE_TIME

EPOCH_OFFSET_PLUS_1_VALUE

EPOCH_OFFSET_VALUE

EXCEL_TIME

FROM_MAX_VALUE

FROM_MIN_VALUE

ICU4C_TIME

JAVA_TIME

MAC_OLD_TIME

MAC_TIME

MAX_SCALE

TO_MAX_VALUE

TO_MIN_VALUE

UNITS_VALUE

UNIX_MICROSECONDS_TIME

UNIX_TIME

WINDOWS_FILE_TIME

方法详细资料

from

bigDecimalFrom

bigDecimalFrom

bigDecimalFrom

toLong

toBigDecimal

toBigDecimal

getTimeScaleValue