| java.lang.Object
 com.ibm.icu.util.UniversalTimeScale
| UniversalTimeScale | | final public class UniversalTimeScale (Code) | | 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.
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| Field Summary | |
| final public static int | DB2_TIME
Used in DB2. | | final public static int | DOTNET_DATE_TIME
Used in the .NET framework's System.DateTime structure.
Data is a long. | | final public static int | EPOCH_OFFSET_MINUS_1_VALUE
The constant used to select the epoch offset minus one value
for a time scale.
NOTE: This is an internal value. | | final public static 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. | | final public static int | EPOCH_OFFSET_VALUE
The constant used to select the epoch offset value
for a time scale. | | final public static int | EXCEL_TIME
Used in Excel. | | final public static int | FROM_MAX_VALUE
The constant used to select the maximum from value
for a time scale. | | final public static int | FROM_MIN_VALUE
The constant used to select the minimum from value
for a time scale. | | final public static int | ICU4C_TIME
Used in the ICU4C. | | final public static int | JAVA_TIME
Used in the JDK. | | final public static int | MAC_OLD_TIME
Used in older Macintosh systems. | | final public static int | MAC_TIME
Used in the JDK. | | final public static int | MAX_ROUND_VALUE
The constant used to select the maximum safe rounding value
for a time scale.
NOTE: This is an internal value. | | final public static int | MAX_SCALE
This is the first unused time scale value. | | final public static int | MAX_SCALE_VALUE
The number of time scale values.
NOTE: This is an internal value. | | final public static int | MIN_ROUND_VALUE
The constant used to select the minimum safe rounding value
for a time scale.
NOTE: This is an internal value. | | final public static int | TO_MAX_VALUE
The constant used to select the maximum to value
for a time scale. | | final public static int | TO_MIN_VALUE
The constant used to select the minimum to value
for a time scale. | | final public static int | UNITS_ROUND_VALUE
The constant used to select the units round value
for a time scale.
NOTE: This is an internal value. | | final public static int | UNITS_VALUE
The constant used to select the units value
for a time scale. | | final public static int | UNIX_TIME
Used in Unix systems. | | final public static int | WINDOWS_FILE_TIME
Used in Windows for file times. |
| Method Summary | |
| public static BigDecimal | bigDecimalFrom(double otherTime, int timeScale)
Convert a double datetime from the given time scale to the universal time scale. | | public static BigDecimal | bigDecimalFrom(long otherTime, int timeScale)
Convert a long datetime from the given time scale to the universal time scale. | | public static BigDecimal | bigDecimalFrom(BigDecimal otherTime, int timeScale)
Convert a BigDecimal datetime from the given time scale to the universal time scale. | | public static long | from(long otherTime, int timeScale)
Convert a long datetime from the given time scale to the universal time scale. | | public static long | getTimeScaleValue(int scale, int value)
Get a value associated with a particular time scale. | | public static BigDecimal | toBigDecimal(long universalTime, int timeScale)
Convert a datetime from the universal time scale to a BigDecimal in the given time scale. | | public static BigDecimal | toBigDecimal(BigDecimal universalTime, int timeScale)
Convert a datetime from the universal time scale to a BigDecimal in the given time scale. | | public static BigDecimal | toBigDecimalTrunc(BigDecimal universalTime, int timeScale)
Convert a time in the Universal Time Scale into another time
scale. | | 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. |
| DB2_TIME | | final public static int DB2_TIME(Code) | | Used in DB2. Data is a ?unknown?. Value
is days since December 31, 1899.
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| DOTNET_DATE_TIME | | final public static int DOTNET_DATE_TIME(Code) | | Used in the .NET framework's System.DateTime structure.
Data is a long. Value is ticks (1 tick == 100 nanoseconds) since January 1, 0001.
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| EPOCH_OFFSET_MINUS_1_VALUE | | final public static int EPOCH_OFFSET_MINUS_1_VALUE(Code) | | 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: UniversalTimeScale.getTimeScaleValue |
| EPOCH_OFFSET_PLUS_1_VALUE | | final public static int EPOCH_OFFSET_PLUS_1_VALUE(Code) | | 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: UniversalTimeScale.getTimeScaleValue |
| EXCEL_TIME | | final public static int EXCEL_TIME(Code) | | Used in Excel. Data is a ?unknown?. Value
is days since December 31, 1899.
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| ICU4C_TIME | | final public static int ICU4C_TIME(Code) | | Used in the ICU4C. Data is a double. Value
is milliseconds since January 1, 1970.
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| JAVA_TIME | | final public static int JAVA_TIME(Code) | | Used in the JDK. Data is a long. Value
is milliseconds since January 1, 1970.
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| MAC_OLD_TIME | | final public static int MAC_OLD_TIME(Code) | | Used in older Macintosh systems. Data is an int. Value
is seconds since January 1, 1904.
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| MAC_TIME | | final public static int MAC_TIME(Code) | | Used in the JDK. Data is a double. Value
is milliseconds since January 1, 2001.
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| MAX_ROUND_VALUE | | final public static int MAX_ROUND_VALUE(Code) | | 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: UniversalTimeScale.getTimeScaleValue |
| MAX_SCALE | | final public static int MAX_SCALE(Code) | | This is the first unused time scale value.
|
| MIN_ROUND_VALUE | | final public static int MIN_ROUND_VALUE(Code) | | 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: UniversalTimeScale.getTimeScaleValue |
| UNITS_ROUND_VALUE | | final public static int UNITS_ROUND_VALUE(Code) | | 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: UniversalTimeScale.getTimeScaleValue |
| UNITS_VALUE | | final public static int UNITS_VALUE(Code) | | The constant used to select the units value
for a time scale.
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| UNIX_TIME | | final public static int UNIX_TIME(Code) | | Used in Unix systems. Data is an int or a long. Value
is seconds since January 1, 1970.
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| WINDOWS_FILE_TIME | | final public static int WINDOWS_FILE_TIME(Code) | | Used in Windows for file times. Data is a long. Value
is ticks (1 tick == 100 nanoseconds) since January 1, 1601.
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| bigDecimalFrom | | public static BigDecimal bigDecimalFrom(double otherTime, int timeScale)(Code) | | 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
Parameters:
timeScale - The time scale to convert from The datetime converted to the universal time scale |
| bigDecimalFrom | | public static BigDecimal bigDecimalFrom(long otherTime, int timeScale)(Code) | | 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
Parameters:
timeScale - The time scale to convert from The datetime converted to the universal time scale |
| bigDecimalFrom | | public static BigDecimal bigDecimalFrom(BigDecimal otherTime, int timeScale)(Code) | | 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
Parameters:
timeScale - The time scale to convert from The datetime converted to the universal time scale |
| from | | public static long from(long otherTime, int timeScale)(Code) | | Convert a long datetime from the given time scale to the universal time scale.
Parameters:
otherTime - The long datetime
Parameters:
timeScale - The time scale to convert from The datetime converted to the universal time scale |
| getTimeScaleValue | | public static long getTimeScaleValue(int scale, int value)(Code) | | Get a value associated with a particular time scale.
Parameters:
scale - - the time scale
Parameters:
value - - a constant representing the value to get - the value. |
| toBigDecimal | | public static BigDecimal toBigDecimal(long universalTime, int timeScale)(Code) | | 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
Parameters:
timeScale - The time scale to convert to The datetime converted to the given time scale |
| toBigDecimal | | public static BigDecimal toBigDecimal(BigDecimal universalTime, int timeScale)(Code) | | 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
Parameters:
timeScale - The time scale to convert to The datetime converted to the given time scale |
| toBigDecimalTrunc | | public static BigDecimal toBigDecimalTrunc(BigDecimal universalTime, int timeScale)(Code) | | 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
Parameters:
timeScale - the time scale to convert to the time in the given time scale |
| toLong | | public static long toLong(long universalTime, int timeScale)(Code) | | 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
Parameters:
timeScale - The time scale to convert to The datetime converted to the given time scale |
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