public final class Period extends Object implements ChronoPeriod, Serializable
This class models a quantity or amount of time in terms of years, months and days.
See Duration
for the timebased equivalent to this class.
Durations and periods differ in their treatment of daylight savings time
when added to ZonedDateTime
. A Duration
will add an exact
number of seconds, thus a duration of one day is always exactly 24 hours.
By contrast, a Period
will add a conceptual day, trying to maintain
the local time.
For example, consider adding a period of one day and a duration of one day to
18:00 on the evening before a daylight savings gap. The Period
will add
the conceptual day and result in a ZonedDateTime
at 18:00 the following day.
By contrast, the Duration
will add exactly 24 hours, resulting in a
ZonedDateTime
at 19:00 the following day (assuming a one hour DST gap).
The supported units of a period are YEARS
,
MONTHS
and DAYS
.
All three fields are always present, but may be set to zero.
The ISO8601 calendar system is the modern civil calendar system used today in most of the world. It is equivalent to the proleptic Gregorian calendar system, in which today's rules for leap years are applied for all time.
The period is modeled as a directed amount of time, meaning that individual parts of the period may be negative.
This is a valuebased
class; use of identitysensitive operations (including reference equality
(==
), identity hash code, or synchronization) on instances of
Period
may have unpredictable results and should be avoided.
The equals
method should be used for comparisons.
Modifier and Type  Field and Description 

static Period 
ZERO
A constant for a period of zero.

Modifier and Type  Method and Description 

Temporal 
addTo(Temporal temporal)
Adds this period to the specified temporal object.

static Period 
between(LocalDate startDateInclusive,
LocalDate endDateExclusive)
Obtains a
Period consisting of the number of years, months,
and days between two dates. 
boolean 
equals(Object obj)
Checks if this period is equal to another period.

static Period 
from(TemporalAmount amount)
Obtains an instance of
Period from a temporal amount. 
long 
get(TemporalUnit unit)
Gets the value of the requested unit.

IsoChronology 
getChronology()
Gets the chronology of this period, which is the ISO calendar system.

int 
getDays()
Gets the amount of days of this period.

int 
getMonths()
Gets the amount of months of this period.

List<TemporalUnit> 
getUnits()
Gets the set of units supported by this period.

int 
getYears()
Gets the amount of years of this period.

int 
hashCode()
A hash code for this period.

boolean 
isNegative()
Checks if any of the three units of this period are negative.

boolean 
isZero()
Checks if all three units of this period are zero.

Period 
minus(TemporalAmount amountToSubtract)
Returns a copy of this period with the specified period subtracted.

Period 
minusDays(long daysToSubtract)
Returns a copy of this period with the specified days subtracted.

Period 
minusMonths(long monthsToSubtract)
Returns a copy of this period with the specified months subtracted.

Period 
minusYears(long yearsToSubtract)
Returns a copy of this period with the specified years subtracted.

Period 
multipliedBy(int scalar)
Returns a new instance with each element in this period multiplied
by the specified scalar.

Period 
negated()
Returns a new instance with each amount in this period negated.

Period 
normalized()
Returns a copy of this period with the years and months normalized.

static Period 
of(int years,
int months,
int days)
Obtains a
Period representing a number of years, months and days. 
static Period 
ofDays(int days)
Obtains a
Period representing a number of days. 
static Period 
ofMonths(int months)
Obtains a
Period representing a number of months. 
static Period 
ofWeeks(int weeks)
Obtains a
Period representing a number of weeks. 
static Period 
ofYears(int years)
Obtains a
Period representing a number of years. 
static Period 
parse(CharSequence text)
Obtains a
Period from a text string such as PnYnMnD . 
Period 
plus(TemporalAmount amountToAdd)
Returns a copy of this period with the specified period added.

Period 
plusDays(long daysToAdd)
Returns a copy of this period with the specified days added.

Period 
plusMonths(long monthsToAdd)
Returns a copy of this period with the specified months added.

Period 
plusYears(long yearsToAdd)
Returns a copy of this period with the specified years added.

Temporal 
subtractFrom(Temporal temporal)
Subtracts this period from the specified temporal object.

String 
toString()
Outputs this period as a
String , such as P6Y3M1D . 
long 
toTotalMonths()
Gets the total number of months in this period.

Period 
withDays(int days)
Returns a copy of this period with the specified amount of days.

Period 
withMonths(int months)
Returns a copy of this period with the specified amount of months.

Period 
withYears(int years)
Returns a copy of this period with the specified amount of years.

clone, finalize, getClass, notify, notifyAll, wait, wait, wait
between
public static final Period ZERO
public static Period ofYears(int years)
Period
representing a number of years.
The resulting period will have the specified years. The months and days units will be zero.
years
 the number of years, positive or negativepublic static Period ofMonths(int months)
Period
representing a number of months.
The resulting period will have the specified months. The years and days units will be zero.
months
 the number of months, positive or negativepublic static Period ofWeeks(int weeks)
Period
representing a number of weeks.
The resulting period will be daybased, with the amount of days equal to the number of weeks multiplied by 7. The years and months units will be zero.
weeks
 the number of weeks, positive or negativepublic static Period ofDays(int days)
Period
representing a number of days.
The resulting period will have the specified days. The years and months units will be zero.
days
 the number of days, positive or negativepublic static Period of(int years, int months, int days)
Period
representing a number of years, months and days.
This creates an instance based on years, months and days.
years
 the amount of years, may be negativemonths
 the amount of months, may be negativedays
 the amount of days, may be negativepublic static Period from(TemporalAmount amount)
Period
from a temporal amount.
This obtains a period based on the specified amount.
A TemporalAmount
represents an amount of time, which may be
datebased or timebased, which this factory extracts to a Period
.
The conversion loops around the set of units from the amount and uses
the YEARS
, MONTHS
and DAYS
units to create a period.
If any other units are found then an exception is thrown.
If the amount is a ChronoPeriod
then it must use the ISO chronology.
amount
 the temporal amount to convert, not nullDateTimeException
 if unable to convert to a Period
ArithmeticException
 if the amount of years, months or days exceeds an intpublic static Period parse(CharSequence text)
Period
from a text string such as PnYnMnD
.
This will parse the string produced by toString()
which is
based on the ISO8601 period formats PnYnMnD
and PnW
.
The string starts with an optional sign, denoted by the ASCII negative
or positive symbol. If negative, the whole period is negated.
The ASCII letter "P" is next in upper or lower case.
There are then four sections, each consisting of a number and a suffix.
At least one of the four sections must be present.
The sections have suffixes in ASCII of "Y", "M", "W" and "D" for
years, months, weeks and days, accepted in upper or lower case.
The suffixes must occur in order.
The number part of each section must consist of ASCII digits.
The number may be prefixed by the ASCII negative or positive symbol.
The number must parse to an int
.
The leading plus/minus sign, and negative values for other units are
not part of the ISO8601 standard. In addition, ISO8601 does not
permit mixing between the PnYnMnD
and PnW
formats.
Any weekbased input is multiplied by 7 and treated as a number of days.
For example, the following are valid inputs:
"P2Y"  Period.ofYears(2) "P3M"  Period.ofMonths(3) "P4W"  Period.ofWeeks(4) "P5D"  Period.ofDays(5) "P1Y2M3D"  Period.of(1, 2, 3) "P1Y2M3W4D"  Period.of(1, 2, 25) "P1Y2M"  Period.of(1, 2, 0) "P1Y2M"  Period.of(1, 2, 0)
text
 the text to parse, not nullDateTimeParseException
 if the text cannot be parsed to a periodpublic static Period between(LocalDate startDateInclusive, LocalDate endDateExclusive)
Period
consisting of the number of years, months,
and days between two dates.
The start date is included, but the end date is not.
The period is calculated by removing complete months, then calculating
the remaining number of days, adjusting to ensure that both have the same sign.
The number of months is then split into years and months based on a 12 month year.
A month is considered if the end dayofmonth is greater than or equal to the start dayofmonth.
For example, from 20100115
to 20110318
is one year, two months and three days.
The result of this method can be a negative period if the end is before the start. The negative sign will be the same in each of year, month and day.
startDateInclusive
 the start date, inclusive, not nullendDateExclusive
 the end date, exclusive, not nullChronoLocalDate.until(ChronoLocalDate)
public long get(TemporalUnit unit)
This returns a value for each of the three supported units,
YEARS
, MONTHS
and
DAYS
.
All other units throw an exception.
get
in interface ChronoPeriod
get
in interface TemporalAmount
unit
 the TemporalUnit
for which to return the valueDateTimeException
 if the unit is not supportedUnsupportedTemporalTypeException
 if the unit is not supportedpublic List<TemporalUnit> getUnits()
The supported units are YEARS
,
MONTHS
and DAYS
.
They are returned in the order years, months, days.
This set can be used in conjunction with get(TemporalUnit)
to access the entire state of the period.
getUnits
in interface ChronoPeriod
getUnits
in interface TemporalAmount
public IsoChronology getChronology()
The Chronology
represents the calendar system in use.
The ISO8601 calendar system is the modern civil calendar system used today
in most of the world. It is equivalent to the proleptic Gregorian calendar
system, in which today's rules for leap years are applied for all time.
getChronology
in interface ChronoPeriod
public boolean isZero()
A zero period has the value zero for the years, months and days units.
isZero
in interface ChronoPeriod
public boolean isNegative()
This checks whether the years, months or days units are less than zero.
isNegative
in interface ChronoPeriod
public int getYears()
This returns the years unit.
The months unit is not automatically normalized with the years unit. This means that a period of "15 months" is different to a period of "1 year and 3 months".
public int getMonths()
This returns the months unit.
The months unit is not automatically normalized with the years unit. This means that a period of "15 months" is different to a period of "1 year and 3 months".
public int getDays()
This returns the days unit.
public Period withYears(int years)
This sets the amount of the years unit in a copy of this period. The months and days units are unaffected.
The months unit is not automatically normalized with the years unit. This means that a period of "15 months" is different to a period of "1 year and 3 months".
This instance is immutable and unaffected by this method call.
years
 the years to represent, may be negativePeriod
based on this period with the requested years, not nullpublic Period withMonths(int months)
This sets the amount of the months unit in a copy of this period. The years and days units are unaffected.
The months unit is not automatically normalized with the years unit. This means that a period of "15 months" is different to a period of "1 year and 3 months".
This instance is immutable and unaffected by this method call.
months
 the months to represent, may be negativePeriod
based on this period with the requested months, not nullpublic Period withDays(int days)
This sets the amount of the days unit in a copy of this period. The years and months units are unaffected.
This instance is immutable and unaffected by this method call.
days
 the days to represent, may be negativePeriod
based on this period with the requested days, not nullpublic Period plus(TemporalAmount amountToAdd)
This operates separately on the years, months and days. No normalization is performed.
For example, "1 year, 6 months and 3 days" plus "2 years, 2 months and 2 days" returns "3 years, 8 months and 5 days".
The specified amount is typically an instance of Period
.
Other types are interpreted using from(TemporalAmount)
.
This instance is immutable and unaffected by this method call.
plus
in interface ChronoPeriod
amountToAdd
 the period to add, not nullPeriod
based on this period with the requested period added, not nullDateTimeException
 if the specified amount has a nonISO chronology or
contains an invalid unitArithmeticException
 if numeric overflow occurspublic Period plusYears(long yearsToAdd)
This adds the amount to the years unit in a copy of this period. The months and days units are unaffected. For example, "1 year, 6 months and 3 days" plus 2 years returns "3 years, 6 months and 3 days".
This instance is immutable and unaffected by this method call.
yearsToAdd
 the years to add, positive or negativePeriod
based on this period with the specified years added, not nullArithmeticException
 if numeric overflow occurspublic Period plusMonths(long monthsToAdd)
This adds the amount to the months unit in a copy of this period. The years and days units are unaffected. For example, "1 year, 6 months and 3 days" plus 2 months returns "1 year, 8 months and 3 days".
This instance is immutable and unaffected by this method call.
monthsToAdd
 the months to add, positive or negativePeriod
based on this period with the specified months added, not nullArithmeticException
 if numeric overflow occurspublic Period plusDays(long daysToAdd)
This adds the amount to the days unit in a copy of this period. The years and months units are unaffected. For example, "1 year, 6 months and 3 days" plus 2 days returns "1 year, 6 months and 5 days".
This instance is immutable and unaffected by this method call.
daysToAdd
 the days to add, positive or negativePeriod
based on this period with the specified days added, not nullArithmeticException
 if numeric overflow occurspublic Period minus(TemporalAmount amountToSubtract)
This operates separately on the years, months and days. No normalization is performed.
For example, "1 year, 6 months and 3 days" minus "2 years, 2 months and 2 days" returns "1 years, 4 months and 1 day".
The specified amount is typically an instance of Period
.
Other types are interpreted using from(TemporalAmount)
.
This instance is immutable and unaffected by this method call.
minus
in interface ChronoPeriod
amountToSubtract
 the period to subtract, not nullPeriod
based on this period with the requested period subtracted, not nullDateTimeException
 if the specified amount has a nonISO chronology or
contains an invalid unitArithmeticException
 if numeric overflow occurspublic Period minusYears(long yearsToSubtract)
This subtracts the amount from the years unit in a copy of this period. The months and days units are unaffected. For example, "1 year, 6 months and 3 days" minus 2 years returns "1 years, 6 months and 3 days".
This instance is immutable and unaffected by this method call.
yearsToSubtract
 the years to subtract, positive or negativePeriod
based on this period with the specified years subtracted, not nullArithmeticException
 if numeric overflow occurspublic Period minusMonths(long monthsToSubtract)
This subtracts the amount from the months unit in a copy of this period. The years and days units are unaffected. For example, "1 year, 6 months and 3 days" minus 2 months returns "1 year, 4 months and 3 days".
This instance is immutable and unaffected by this method call.
monthsToSubtract
 the years to subtract, positive or negativePeriod
based on this period with the specified months subtracted, not nullArithmeticException
 if numeric overflow occurspublic Period minusDays(long daysToSubtract)
This subtracts the amount from the days unit in a copy of this period. The years and months units are unaffected. For example, "1 year, 6 months and 3 days" minus 2 days returns "1 year, 6 months and 1 day".
This instance is immutable and unaffected by this method call.
daysToSubtract
 the months to subtract, positive or negativePeriod
based on this period with the specified days subtracted, not nullArithmeticException
 if numeric overflow occurspublic Period multipliedBy(int scalar)
This returns a period with each of the years, months and days units individually multiplied. For example, a period of "2 years, 3 months and 4 days" multiplied by 3 will return "6 years, 9 months and 12 days". No normalization is performed.
multipliedBy
in interface ChronoPeriod
scalar
 the scalar to multiply by, not nullPeriod
based on this period with the amounts multiplied by the scalar, not nullArithmeticException
 if numeric overflow occurspublic Period negated()
This returns a period with each of the years, months and days units individually negated. For example, a period of "2 years, 3 months and 4 days" will be negated to "2 years, 3 months and 4 days". No normalization is performed.
negated
in interface ChronoPeriod
Period
based on this period with the amounts negated, not nullArithmeticException
 if numeric overflow occurs, which only happens if
one of the units has the value Long.MIN_VALUE
public Period normalized()
This normalizes the years and months units, leaving the days unit unchanged. The months unit is adjusted to have an absolute value less than 11, with the years unit being adjusted to compensate. For example, a period of "1 Year and 15 months" will be normalized to "2 years and 3 months".
The sign of the years and months units will be the same after normalization. For example, a period of "1 year and 25 months" will be normalized to "1 year and 1 month".
This instance is immutable and unaffected by this method call.
normalized
in interface ChronoPeriod
Period
based on this period with excess months normalized to years, not nullArithmeticException
 if numeric overflow occurspublic long toTotalMonths()
This returns the total number of months in the period by multiplying the number of years by 12 and adding the number of months.
This instance is immutable and unaffected by this method call.
public Temporal addTo(Temporal temporal)
This returns a temporal object of the same observable type as the input with this period added. If the temporal has a chronology, it must be the ISO chronology.
In most cases, it is clearer to reverse the calling pattern by using
Temporal.plus(TemporalAmount)
.
// these two lines are equivalent, but the second approach is recommended dateTime = thisPeriod.addTo(dateTime); dateTime = dateTime.plus(thisPeriod);
The calculation operates as follows. First, the chronology of the temporal is checked to ensure it is ISO chronology or null. Second, if the months are zero, the years are added if nonzero, otherwise the combination of years and months is added if nonzero. Finally, any days are added.
This approach ensures that a partial period can be added to a partial date.
For example, a period of years and/or months can be added to a YearMonth
,
but a period including days cannot.
The approach also adds years and months together when necessary, which ensures
correct behaviour at the end of the month.
This instance is immutable and unaffected by this method call.
addTo
in interface ChronoPeriod
addTo
in interface TemporalAmount
temporal
 the temporal object to adjust, not nullDateTimeException
 if unable to addArithmeticException
 if numeric overflow occurspublic Temporal subtractFrom(Temporal temporal)
This returns a temporal object of the same observable type as the input with this period subtracted. If the temporal has a chronology, it must be the ISO chronology.
In most cases, it is clearer to reverse the calling pattern by using
Temporal.minus(TemporalAmount)
.
// these two lines are equivalent, but the second approach is recommended dateTime = thisPeriod.subtractFrom(dateTime); dateTime = dateTime.minus(thisPeriod);
The calculation operates as follows. First, the chronology of the temporal is checked to ensure it is ISO chronology or null. Second, if the months are zero, the years are subtracted if nonzero, otherwise the combination of years and months is subtracted if nonzero. Finally, any days are subtracted.
This approach ensures that a partial period can be subtracted from a partial date.
For example, a period of years and/or months can be subtracted from a YearMonth
,
but a period including days cannot.
The approach also subtracts years and months together when necessary, which ensures
correct behaviour at the end of the month.
This instance is immutable and unaffected by this method call.
subtractFrom
in interface ChronoPeriod
subtractFrom
in interface TemporalAmount
temporal
 the temporal object to adjust, not nullDateTimeException
 if unable to subtractArithmeticException
 if numeric overflow occurspublic boolean equals(Object obj)
The comparison is based on the type Period
and each of the three amounts.
To be equal, the years, months and days units must be individually equal.
Note that this means that a period of "15 Months" is not equal to a period
of "1 Year and 3 Months".
equals
in interface ChronoPeriod
equals
in class Object
obj
 the object to check, null returns falseObject.hashCode()
,
HashMap
public int hashCode()
hashCode
in interface ChronoPeriod
hashCode
in class Object
Object.equals(java.lang.Object)
,
System.identityHashCode(java.lang.Object)
public String toString()
String
, such as P6Y3M1D
.
The output will be in the ISO8601 period format. A zero period will be represented as zero days, 'P0D'.
toString
in interface ChronoPeriod
toString
in class Object