UniversalTimeScale
class UniversalTimeScale
| kotlin.Any | |
| ↳ | android.icu.util.UniversalTimeScale |
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.
Summary
| Constants | |
|---|---|
| static Int |
Used in DB2. |
| static Int |
Used in the . |
| static Int |
The constant used to select the epoch plus one value for a time scale. |
| static Int |
The constant used to select the epoch offset value for a time scale. |
| static Int |
Used in Excel. |
| static Int |
The constant used to select the maximum from value for a time scale. |
| static Int |
The constant used to select the minimum from value for a time scale. |
| static Int |
Used in the ICU4C. |
| static Int |
Used in the JDK. |
| static Int |
Used in older Macintosh systems. |
| static Int |
Used in the JDK. |
| static Int |
This is the first unused time scale value. |
| static Int |
The constant used to select the maximum to value for a time scale. |
| static Int |
The constant used to select the minimum to value for a time scale. |
| static Int |
The constant used to select the units value for a time scale. |
| static Int |
Data is a |
| static Int |
Used in Unix systems. |
| static Int |
Used in Windows for file times. |
| Public methods | |
|---|---|
| static BigDecimal! |
bigDecimalFrom(otherTime: Double, timeScale: Int)Convert a |
| static BigDecimal! |
bigDecimalFrom(otherTime: Long, timeScale: Int)Convert a |
| static BigDecimal! |
bigDecimalFrom(otherTime: BigDecimal!, timeScale: Int)Convert a |
| static Long |
Convert a |
| static Long |
getTimeScaleValue(scale: Int, value: Int)Get a value associated with a particular time scale. |
| static BigDecimal! |
toBigDecimal(universalTime: Long, timeScale: Int)Convert a datetime from the universal time scale to a |
| static BigDecimal! |
toBigDecimal(universalTime: BigDecimal!, timeScale: Int)Convert a datetime from the universal time scale to a |
| static Long |
Convert a datetime from the universal time scale stored as a |
Constants
DB2_TIME
static val DB2_TIME: Int
Used in DB2. Data is a ?unknown?. Value is days since December 31, 1899.
Value: 8
DOTNET_DATE_TIME
static val DOTNET_DATE_TIME: Int
Used in the .NET framework's System.DateTime structure. Data is a long. Value is ticks (1 tick == 100 nanoseconds) since January 1, 0001.
Value: 4
EPOCH_OFFSET_PLUS_1_VALUE
static val EPOCH_OFFSET_PLUS_1_VALUE: Int
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.
Value: 6
See Also
EPOCH_OFFSET_VALUE
static val EPOCH_OFFSET_VALUE: Int
The constant used to select the epoch offset value for a time scale.
Value: 1
See Also
EXCEL_TIME
static val EXCEL_TIME: Int
Used in Excel. Data is a ?unknown?. Value is days since December 31, 1899.
Value: 7
FROM_MAX_VALUE
static val FROM_MAX_VALUE: Int
The constant used to select the maximum from value for a time scale.
Value: 3
See Also
FROM_MIN_VALUE
static val FROM_MIN_VALUE: Int
The constant used to select the minimum from value for a time scale.
Value: 2
See Also
ICU4C_TIME
static val ICU4C_TIME: Int
Used in the ICU4C. Data is a double. Value is milliseconds since January 1, 1970.
Value: 2
JAVA_TIME
static val JAVA_TIME: Int
Used in the JDK. Data is a long. Value is milliseconds since January 1, 1970.
Value: 0
MAC_OLD_TIME
static val MAC_OLD_TIME: Int
Used in older Macintosh systems. Data is an int. Value is seconds since January 1, 1904.
Value: 5
MAC_TIME
static val MAC_TIME: Int
Used in the JDK. Data is a double. Value is milliseconds since January 1, 2001.
Value: 6
MAX_SCALE
static valMAX_SCALE: Int
Deprecated: ICU 59
This is the first unused time scale value.
Value: 10
TO_MAX_VALUE
static val TO_MAX_VALUE: Int
The constant used to select the maximum to value for a time scale.
Value: 5
See Also
TO_MIN_VALUE
static val TO_MIN_VALUE: Int
The constant used to select the minimum to value for a time scale.
Value: 4
See Also
UNITS_VALUE
static val UNITS_VALUE: Int
The constant used to select the units value for a time scale.
Value: 0
UNIX_MICROSECONDS_TIME
static val UNIX_MICROSECONDS_TIME: Int
Data is a long. Value is microseconds since January 1, 1970. Similar to Unix time (linear value from 1970) and struct timeval (microseconds resolution).
Value: 9
UNIX_TIME
static val UNIX_TIME: Int
Used in Unix systems. Data is an int or a long. Value is seconds since January 1, 1970.
Value: 1
WINDOWS_FILE_TIME
static val WINDOWS_FILE_TIME: Int
Used in Windows for file times. Data is a long. Value is ticks (1 tick == 100 nanoseconds) since January 1, 1601.
Value: 3
Public methods
bigDecimalFrom
static fun bigDecimalFrom(
otherTime: Double,
timeScale: Int
): BigDecimal!
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 |
Double: The double datetime |
timeScale |
Int: The time scale to convert from |
| Return | |
|---|---|
BigDecimal! |
The datetime converted to the universal time scale |
bigDecimalFrom
static fun bigDecimalFrom(
otherTime: Long,
timeScale: Int
): BigDecimal!
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 |
Long: The long datetime |
timeScale |
Int: The time scale to convert from |
| Return | |
|---|---|
BigDecimal! |
The datetime converted to the universal time scale |
bigDecimalFrom
static fun bigDecimalFrom(
otherTime: BigDecimal!,
timeScale: Int
): BigDecimal!
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 |
BigDecimal!: The BigDecimal datetime |
timeScale |
Int: The time scale to convert from |
| Return | |
|---|---|
BigDecimal! |
The datetime converted to the universal time scale |
from
static fun from(
otherTime: Long,
timeScale: Int
): Long
Convert a long datetime from the given time scale to the universal time scale.
| Parameters | |
|---|---|
otherTime |
Long: The long datetime |
timeScale |
Int: The time scale to convert from |
| Return | |
|---|---|
Long |
The datetime converted to the universal time scale |
getTimeScaleValue
static fun getTimeScaleValue(
scale: Int,
value: Int
): Long
Get a value associated with a particular time scale.
| Parameters | |
|---|---|
scale |
Int: - the time scale |
value |
Int: - a constant representing the value to get |
| Return | |
|---|---|
Long |
- the value. |
toBigDecimal
static fun toBigDecimal(
universalTime: Long,
timeScale: Int
): BigDecimal!
Convert a datetime from the universal time scale to a BigDecimal in the given time scale.
| Parameters | |
|---|---|
universalTime |
Long: The datetime in the universal time scale |
timeScale |
Int: The time scale to convert to |
| Return | |
|---|---|
BigDecimal! |
The datetime converted to the given time scale |
toBigDecimal
static fun toBigDecimal(
universalTime: BigDecimal!,
timeScale: Int
): BigDecimal!
Convert a datetime from the universal time scale to a BigDecimal in the given time scale.
| Parameters | |
|---|---|
universalTime |
BigDecimal!: The datetime in the universal time scale |
timeScale |
Int: The time scale to convert to |
| Return | |
|---|---|
BigDecimal! |
The datetime converted to the given time scale |
toLong
static fun toLong(
universalTime: Long,
timeScale: Int
): Long
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 |
Long: The datetime in the universal time scale |
timeScale |
Int: The time scale to convert to |
| Return | |
|---|---|
Long |
The datetime converted to the given time scale |