Class UniversalTimeScale

java.lang.Object
org.graalvm.shadowed.com.ibm.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.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    DB2_TIME
    Used in DB2.
    static final int
    DOTNET_DATE_TIME
    Used in the .NET framework's System.DateTime structure.
    static final int
    EPOCH_OFFSET_MINUS_1_VALUE
    Deprecated.
    This API is ICU internal only.
    static final int
    EPOCH_OFFSET_PLUS_1_VALUE
    The constant used to select the epoch plus one value for a time scale.
    static final int
    EPOCH_OFFSET_VALUE
    The constant used to select the epoch offset value for a time scale.
    static final int
    EXCEL_TIME
    Used in Excel.
    static final int
    FROM_MAX_VALUE
    The constant used to select the maximum from value for a time scale.
    static final int
    FROM_MIN_VALUE
    The constant used to select the minimum from value for a time scale.
    static final int
    ICU4C_TIME
    Used in the ICU4C.
    static final int
    JAVA_TIME
    Used in the JDK.
    static final int
    MAC_OLD_TIME
    Used in older Macintosh systems.
    static final int
    MAC_TIME
    Used in the JDK.
    static final int
    MAX_ROUND_VALUE
    Deprecated.
    This API is ICU internal only.
    static final int
    MAX_SCALE
    Deprecated.
    ICU 59
    static final int
    MAX_SCALE_VALUE
    Deprecated.
    This API is ICU internal only.
    static final int
    MIN_ROUND_VALUE
    Deprecated.
    This API is ICU internal only.
    static final int
    TO_MAX_VALUE
    The constant used to select the maximum to value for a time scale.
    static final int
    TO_MIN_VALUE
    The constant used to select the minimum to value for a time scale.
    static final int
    UNITS_ROUND_VALUE
    Deprecated.
    This API is ICU internal only.
    static final int
    UNITS_VALUE
    The constant used to select the units value for a time scale.
    static final int
    UNIX_MICROSECONDS_TIME
    Data is a long.
    static final int
    UNIX_TIME
    Used in Unix systems.
    static final int
    WINDOWS_FILE_TIME
    Used in Windows for file times.

  • Method Summary

    Modifier and Type
    Method
    Description
    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 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 a BigDecimal to a long in the given time scale.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • JAVA_TIME

      public static final int JAVA_TIME
      Used in the JDK. Data is a long. Value is milliseconds since January 1, 1970.
      See Also:

    • 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.
      See Also:

    • ICU4C_TIME

      public static final int ICU4C_TIME
      Used in the ICU4C. Data is a double. Value is milliseconds since January 1, 1970.
      See Also:

    • 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.
      See Also:

    • 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.
      See Also:

    • 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.
      See Also:

    • MAC_TIME

      public static final int MAC_TIME
      Used in the JDK. Data is a double. Value is milliseconds since January 1, 2001.
      See Also:

    • EXCEL_TIME

      public static final int EXCEL_TIME
      Used in Excel. Data is a ?unknown?. Value is days since December 31, 1899.
      See Also:

    • DB2_TIME

      public static final int DB2_TIME
      Used in DB2. Data is a ?unknown?. Value is days since December 31, 1899.
      See Also:

    • 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).
      See Also:

    • MAX_SCALE

      @Deprecated public static final int MAX_SCALE
      Deprecated.
      ICU 59
      This is the first unused time scale value.
      See Also:

    • UNITS_VALUE

      public static final int UNITS_VALUE
      The constant used to select the units value for a time scale.
      See Also:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

  • Method Details

    • from

      public static long from(long otherTime, int timeScale)
      Convert a long datetime from the given time scale to the universal time scale.
      Parameters:
      otherTime - The long datetime
      timeScale - The time scale to convert from
      Returns:
      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.
      Parameters:
      otherTime - The double datetime
      timeScale - The time scale to convert from
      Returns:
      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.
      Parameters:
      otherTime - The long datetime
      timeScale - The time scale to convert from
      Returns:
      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.
      Parameters:
      otherTime - The BigDecimal datetime
      timeScale - The time scale to convert from
      Returns:
      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.)

      Parameters:
      universalTime - The datetime in the universal time scale
      timeScale - The time scale to convert to
      Returns:
      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.
      Parameters:
      universalTime - The datetime in the universal time scale
      timeScale - The time scale to convert to
      Returns:
      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.
      Parameters:
      universalTime - The datetime in the universal time scale
      timeScale - The time scale to convert to
      Returns:
      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.
      Parameters:
      scale - - the time scale
      value - - a constant representing the value to get
      Returns:
      - the value.

    • 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 scale
      timeScale - the time scale to convert to
      Returns:
      the time in the given time scale