QDate#
The QDate
class provides date functions. More…
Synopsis#
Functions#
def
__reduce__
()def
__repr__
()def
addDays
(days)def
addMonths
(months)def
addMonths
(months, cal)def
addYears
(years)def
addYears
(years, cal)def
day
()def
day
(cal)def
dayOfWeek
()def
dayOfWeek
(cal)def
dayOfYear
()def
dayOfYear
(cal)def
daysInMonth
()def
daysInMonth
(cal)def
daysInYear
()def
daysInYear
(cal)def
daysTo
(d)def
endOfDay
()def
endOfDay
(spec[, offsetSeconds=0])def
endOfDay
(zone)def
getDate
()def
isNull
()def
isValid
()def
month
()def
month
(cal)def
__ne__
(rhs)def
__lt__
(rhs)def
__le__
(rhs)def
__eq__
(rhs)def
__gt__
(rhs)def
__ge__
(rhs)def
setDate
(year, month, day)def
setDate
(year, month, day, cal)def
startOfDay
()def
startOfDay
(spec[, offsetSeconds=0])def
startOfDay
(zone)def
toJulianDay
()def
toPython
()def
toString
(format[, cal=QCalendar()])def
toString
([format=Qt.TextDate])def
toString
(format[, cal=QCalendar()])def
weekNumber
()def
year
()def
year
(cal)
Static functions#
def
currentDate
()def
fromJulianDay
(jd_)def
fromString
(string, format[, cal=QCalendar()])def
fromString
(string[, format=Qt.TextDate])def
fromString
(string[, format=Qt.TextDate])def
fromString
(string, format[, cal=QCalendar()])def
fromString
(string, format[, cal=QCalendar()])def
isLeapYear
(year)def
isValid
(y, m, d)
Note
This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE
Detailed Description#
A QDate
object represents a particular day, regardless of calendar, locale or other settings used when creating it or supplied by the system. It can report the year, month and day of the month that represent the day with respect to the proleptic Gregorian calendar or any calendar supplied as a QCalendar
object. QDate
objects should be passed by value rather than by reference to const; they simply package qint64
.
A QDate
object is typically created by giving the year, month, and day numbers explicitly. Note that QDate
interprets year numbers less than 100 as presented, i.e., as years 1 through 99, without adding any offset. The static function currentDate()
creates a QDate
object containing the date read from the system clock. An explicit date can also be set using setDate()
. The fromString()
function returns a QDate
given a string and a date format which is used to interpret the date within the string.
The year()
, month()
, and day()
functions provide access to the year, month, and day numbers. When more than one of these values is needed, it is more efficient to call partsFromDate()
, to save repeating (potentially expensive) calendrical calculations.
Also, dayOfWeek()
and dayOfYear()
functions are provided. The same information is provided in textual format by toString()
. QLocale
can map the day numbers to names, QCalendar
can map month numbers to names.
QDate
provides a full set of operators to compare two QDate
objects where smaller means earlier, and larger means later.
You can increment (or decrement) a date by a given number of days using addDays()
. Similarly you can use addMonths()
and addYears()
. The daysTo()
function returns the number of days between two dates.
The daysInMonth()
and daysInYear()
functions return how many days there are in this date’s month and year, respectively. The isLeapYear()
function indicates whether a date is in a leap year. QCalendar
can also supply this information, in some cases more conveniently.
Remarks#
Note
All conversion to and from string formats is done using the C locale. For localized conversions, see QLocale
.
In the Gregorian calendar, there is no year 0. Dates in that year are considered invalid. The year -1 is the year “1 before Christ” or “1 before common era.” The day before 1 January 1 CE, QDate
(1, 1, 1), is 31 December 1 BCE, QDate
(-1, 12, 31). Various other calendars behave similarly; see hasYearZero()
.
Range of Valid Dates#
Dates are stored internally as a Julian Day number, an integer count of every day in a contiguous range, with 24 November 4714 BCE in the Gregorian calendar being Julian Day 0 (1 January 4713 BCE in the Julian calendar). As well as being an efficient and accurate way of storing an absolute date, it is suitable for converting a date into other calendar systems such as Hebrew, Islamic or Chinese. The Julian Day number can be obtained using toJulianDay()
and can be set using fromJulianDay()
.
The range of Julian Day numbers that QDate
can represent is, for technical reasons, limited to between -784350574879 and 784354017364, which means from before 2 billion BCE to after 2 billion CE. This is more than seven times as wide as the range of dates a QDateTime
can represent.
- class PySide6.QtCore.QDate#
PySide6.QtCore.QDate(y, m, d)
PySide6.QtCore.QDate(y, m, d, cal)
- Parameters:
d – int
m – int
cal –
PySide6.QtCore.QCalendar
y – int
Constructs a null date. Null dates are invalid.
Constructs a date with year y
, month m
and day d
.
The date is understood in terms of the Gregorian calendar. If the specified date is invalid, the date is not set and isValid()
returns false
.
- PySide6.QtCore.QDate.__reduce__()#
- Return type:
object
- PySide6.QtCore.QDate.__repr__()#
- Return type:
object
- PySide6.QtCore.QDate.addDays(days)#
- Parameters:
days – int
- Return type:
Returns a QDate
object containing a date ndays
later than the date of this object (or earlier if ndays
is negative).
Returns a null date if the current date is invalid or the new date is out of range.
See also
- PySide6.QtCore.QDate.addMonths(months)#
- Parameters:
months – int
- Return type:
This is an overloaded function.
- PySide6.QtCore.QDate.addMonths(months, cal)
- Parameters:
months – int
cal –
PySide6.QtCore.QCalendar
- Return type:
Returns a QDate
object containing a date nmonths
later than the date of this object (or earlier if nmonths
is negative).
Uses cal
as calendar, if supplied, else the Gregorian calendar.
Note
If the ending day/month combination does not exist in the resulting month/year, this function will return a date that is the latest valid date in the selected month.
See also
- PySide6.QtCore.QDate.addYears(years)#
- Parameters:
years – int
- Return type:
This is an overloaded function.
- PySide6.QtCore.QDate.addYears(years, cal)
- Parameters:
years – int
cal –
PySide6.QtCore.QCalendar
- Return type:
Returns a QDate
object containing a date nyears
later than the date of this object (or earlier if nyears
is negative).
Uses cal
as calendar, if supplied, else the Gregorian calendar.
Note
If the ending day/month combination does not exist in the resulting year (e.g., for the Gregorian calendar, if the date was Feb 29 and the final year is not a leap year), this function will return a date that is the latest valid date in the given month (in the example, Feb 28).
See also
- static PySide6.QtCore.QDate.currentDate()#
- Return type:
Returns the system clock’s current date.
See also
- PySide6.QtCore.QDate.day()#
- Return type:
int
This is an overloaded function.
- PySide6.QtCore.QDate.day(cal)
- Parameters:
cal –
PySide6.QtCore.QCalendar
- Return type:
int
Returns the day of the month for this date.
Uses cal
as calendar if supplied, else the Gregorian calendar (for which the return ranges from 1 to 31). Returns 0 if the date is invalid.
See also
- PySide6.QtCore.QDate.dayOfWeek()#
- Return type:
int
This is an overloaded function.
- PySide6.QtCore.QDate.dayOfWeek(cal)
- Parameters:
cal –
PySide6.QtCore.QCalendar
- Return type:
int
Returns the weekday (1 = Monday to 7 = Sunday) for this date.
Uses cal
as calendar if supplied, else the Gregorian calendar. Returns 0 if the date is invalid. Some calendars may give special meaning (e.g. intercallary days) to values greater than 7.
See also
day()
dayOfYear()
dayOfWeek()
DayOfWeek
- PySide6.QtCore.QDate.dayOfYear()#
- Return type:
int
This is an overloaded function.
- PySide6.QtCore.QDate.dayOfYear(cal)
- Parameters:
cal –
PySide6.QtCore.QCalendar
- Return type:
int
Returns the day of the year (1 for the first day) for this date.
Uses cal
as calendar if supplied, else the Gregorian calendar. Returns 0 if either the date or the first day of its year is invalid.
See also
- PySide6.QtCore.QDate.daysInMonth()#
- Return type:
int
This is an overloaded function.
- PySide6.QtCore.QDate.daysInMonth(cal)
- Parameters:
cal –
PySide6.QtCore.QCalendar
- Return type:
int
Returns the number of days in the month for this date.
Uses cal
as calendar if supplied, else the Gregorian calendar (for which the result ranges from 28 to 31). Returns 0 if the date is invalid.
- PySide6.QtCore.QDate.daysInYear()#
- Return type:
int
This is an overloaded function.
- PySide6.QtCore.QDate.daysInYear(cal)
- Parameters:
cal –
PySide6.QtCore.QCalendar
- Return type:
int
Returns the number of days in the year for this date.
Uses cal
as calendar if supplied, else the Gregorian calendar (for which the result is 365 or 366). Returns 0 if the date is invalid.
- PySide6.QtCore.QDate.daysTo(d)#
- Parameters:
- Return type:
int
Warning
This section contains snippets that were automatically translated from C++ to Python and may contain errors.
Returns the number of days from this date to d
(which is negative if d
is earlier than this date).
Returns 0 if either date is invalid.
Example:
QDate d1(1995, 5, 17) # May 17, 1995 QDate d2(1995, 5, 20) # May 20, 1995 d1.daysTo(d2) # returns 3 d2.daysTo(d1) # returns -3See also
- PySide6.QtCore.QDate.endOfDay()#
- Return type:
This is an overloaded function.
- PySide6.QtCore.QDate.endOfDay(spec[, offsetSeconds=0])
- Parameters:
spec –
TimeSpec
offsetSeconds – int
- Return type:
This is an overloaded function.
Use endOfDay(const QTimeZone &) instead. Returns the end-moment of the day. When a day ends depends on a how time is described: each day starts and ends earlier for those with higher offsets from UTC and later for those with lower offsets from UTC. The time representation to use can be specified either by a \a spec and \a offsetSeconds (ignored unless \a spec is Qt::OffsetSeconds) or by a time zone. Usually, the end of the day is one millisecond before the midnight, 24:00: however, if a local time transition causes the given date to skip over that moment (e.g. a DST spring-forward skipping over 23:00 and the following hour), the actual latest time in the day is returned. When \a spec is Qt::OffsetFromUTC, \a offsetSeconds gives the implied zone's offset from UTC. As UTC and such zones have no transitions, the end of the day is QTime(23, 59, 59, 999) in these cases. In the rare case of a date that was entirely skipped (this happens when a zone east of the international date-line switches to being west of it), the return shall be invalid. Passing Qt::TimeZone as \a spec (instead of passing a QTimeZone) will also produce an invalid result, as shall dates that end outside the range representable by QDateTime.
- PySide6.QtCore.QDate.endOfDay(zone)
- Parameters:
zone –
PySide6.QtCore.QTimeZone
- Return type:
Returns the end-moment of the day.
When a day ends depends on a how time is described: each day starts and ends earlier for those in time-zones further west and later for those in time-zones further east. The time representation to use can be specified by an optional time zone
. The default time representation is the system’s local time.
Usually, the end of the day is one millisecond before the midnight, 24:00: however, if a time-zone transition causes the given date to skip over that moment (e.g. a DST spring-forward skipping over 23:00 and the following hour), the actual latest time in the day is returned. This can only arise when the time representation is a time-zone or local time.
When zone
has a timeSpec() of OffsetFromUTC
or UTC
, the time representation has no transitions so the end of the day is QTime
(23, 59, 59, 999).
In the rare case of a date that was entirely skipped (this happens when a zone east of the international date-line switches to being west of it), the return shall be invalid. Passing an invalid time-zone as zone
will also produce an invalid result, as shall dates that end outside the range representable by QDateTime
.
See also
- static PySide6.QtCore.QDate.fromJulianDay(jd_)#
- Parameters:
jd – int
- Return type:
Converts the Julian day jd
to a QDate
.
See also
- static PySide6.QtCore.QDate.fromString(string, format[, cal=QCalendar()])#
- Parameters:
string – str
format – str
cal –
PySide6.QtCore.QCalendar
- Return type:
Warning
This section contains snippets that were automatically translated from C++ to Python and may contain errors.
Returns the QDate
represented by the string
, using the format
given, or an invalid date if the string cannot be parsed.
Uses cal
as calendar if supplied, else the Gregorian calendar. Ranges of values in the format descriptions below are for the latter; they may be different for other calendars.
These expressions may be used for the format:
Expression
Output
d
The day as a number without a leading zero (1 to 31)
dd
The day as a number with a leading zero (01 to 31)
ddd
The abbreviated day name (‘Mon’ to ‘Sun’).
dddd
The long day name (‘Monday’ to ‘Sunday’).
M
The month as a number without a leading zero (1 to 12)
MM
The month as a number with a leading zero (01 to 12)
MMM
The abbreviated month name (‘Jan’ to ‘Dec’).
MMMM
The long month name (‘January’ to ‘December’).
yy
The year as a two digit number (00 to 99)
yyyy
The year as a four digit number, possibly plus a leading minus sign for negative years.
Note
Day and month names must be given in English (C locale). If localized month and day names are to be recognized, use system()
.toDate().
All other input characters will be treated as text. Any non-empty sequence of characters enclosed in single quotes will also be treated (stripped of the quotes) as text and not be interpreted as expressions. For example:
date = QDate.fromString("1MM12car2003", "d'MM'MMcaryyyy") # date is 1 December 2003
If the format is not satisfied, an invalid QDate
is returned. The expressions that don’t expect leading zeroes (d, M) will be greedy. This means that they will use two digits even if this will put them outside the accepted range of values and leaves too few digits for other sections. For example, the following format string could have meant January 30 but the M will grab two digits, resulting in an invalid date:
date = QDate.fromString("130", "Md") # invalid()
For any field that is not represented in the format the following defaults are used:
Field
Default value
Year
1900
Month
1 (January)
Day
1
The following examples demonstrate the default values:
QDate.fromString("1.30", "M.d") # January 30 1900 QDate.fromString("20000110", "yyyyMMdd") # January 10, 2000 QDate.fromString("20000110", "yyyyMd") # January 10, 2000
Note
If a format character is repeated more times than the longest expression in the table above using it, this part of the format will be read as several expressions with no separator between them; the longest above, possibly repeated as many times as there are copies of it, ending with a residue that may be a shorter expression. Thus 'MMMMMMMMMM'
would match "MayMay05"
and set the month to May. Likewise, 'MMMMMM'
would match "May08"
and find it inconsistent, leading to an invalid date.
See also
- static PySide6.QtCore.QDate.fromString(string[, format=Qt.TextDate])
- Parameters:
string – str
format –
DateFormat
- Return type:
Returns the QDate
represented by the string
, using the format
given, or an invalid date if the string cannot be parsed.
Note for TextDate
: only English month names (e.g. “Jan” in short form or “January” in long form) are recognized.
See also
- static PySide6.QtCore.QDate.fromString(string[, format=Qt.TextDate])
- Parameters:
string – str
format –
DateFormat
- Return type:
This is an overloaded function.
- static PySide6.QtCore.QDate.fromString(string, format[, cal=QCalendar()])
- Parameters:
string – str
format – str
cal –
PySide6.QtCore.QCalendar
- Return type:
This is an overloaded function.
- static PySide6.QtCore.QDate.fromString(string, format[, cal=QCalendar()])
- Parameters:
string – str
format – str
cal –
PySide6.QtCore.QCalendar
- Return type:
This is an overloaded function.
- PySide6.QtCore.QDate.getDate()#
- Return type:
(year, month, day)
Extracts the date’s year, month, and day, and assigns them to *``year``, *``month``, and *``day``. The pointers may be null.
Returns 0 if the date is invalid.
Note
In Qt versions prior to 5.7, this function is marked as non-const
.
See also
- static PySide6.QtCore.QDate.isLeapYear(year)#
- Parameters:
year – int
- Return type:
bool
Returns true
if the specified year
is a leap year in the Gregorian calendar; otherwise returns false
.
See also
- PySide6.QtCore.QDate.isNull()#
- Return type:
bool
Returns true
if the date is null; otherwise returns false
. A null date is invalid.
- PySide6.QtCore.QDate.isValid()#
- Return type:
bool
Returns true
if this date is valid; otherwise returns false
.
See also
- static PySide6.QtCore.QDate.isValid(y, m, d)
- Parameters:
y – int
m – int
d – int
- Return type:
bool
Warning
This section contains snippets that were automatically translated from C++ to Python and may contain errors.
This is an overloaded function.
Returns true
if the specified date (year
, month
, and day
) is valid in the Gregorian calendar; otherwise returns false
.
Example:
QDate.isValid(2002, 5, 17) # true QDate.isValid(2002, 2, 30) # false (Feb 30 does not exist) QDate.isValid(2004, 2, 29) # true (2004 is a leap year) QDate.isValid(2000, 2, 29) # true (2000 is a leap year) QDate.isValid(2006, 2, 29) # false (2006 is not a leap year) QDate.isValid(2100, 2, 29) # false (2100 is not a leap year) QDate.isValid(1202, 6, 6) # true (even though 1202 is pre-Gregorian)See also
- PySide6.QtCore.QDate.month()#
- Return type:
int
This is an overloaded function.
- PySide6.QtCore.QDate.month(cal)
- Parameters:
cal –
PySide6.QtCore.QCalendar
- Return type:
int
Returns the month-number for the date.
Numbers the months of the year starting with 1 for the first. Uses cal
as calendar if supplied, else the Gregorian calendar, for which the month numbering is as follows:
1 = “January”
2 = “February”
3 = “March”
4 = “April”
5 = “May”
6 = “June”
7 = “July”
8 = “August”
9 = “September”
10 = “October”
11 = “November”
12 = “December”
Returns 0 if the date is invalid. Note that some calendars may have more than 12 months in some years.
See also
- PySide6.QtCore.QDate.__ne__(rhs)#
- Parameters:
rhs –
PySide6.QtCore.QDate
- Return type:
bool
Returns true
if lhs
and rhs
represent distinct days; otherwise returns false
.
See also
operator==()
- PySide6.QtCore.QDate.__lt__(rhs)#
- Parameters:
rhs –
PySide6.QtCore.QDate
- Return type:
bool
Returns true
if lhs
is earlier than rhs
; otherwise returns false
.
- PySide6.QtCore.QDate.__le__(rhs)#
- Parameters:
rhs –
PySide6.QtCore.QDate
- Return type:
bool
Returns true
if lhs
is earlier than or equal to rhs
; otherwise returns false
.
- PySide6.QtCore.QDate.__eq__(rhs)#
- Parameters:
rhs –
PySide6.QtCore.QDate
- Return type:
bool
Returns true
if lhs
and rhs
represent the same day, otherwise false
.
- PySide6.QtCore.QDate.__gt__(rhs)#
- Parameters:
rhs –
PySide6.QtCore.QDate
- Return type:
bool
Returns true
if lhs
is later than rhs
; otherwise returns false
.
- PySide6.QtCore.QDate.__ge__(rhs)#
- Parameters:
rhs –
PySide6.QtCore.QDate
- Return type:
bool
Returns true
if lhs
is later than or equal to rhs
; otherwise returns false
.
- PySide6.QtCore.QDate.setDate(year, month, day)#
- Parameters:
year – int
month – int
day – int
- Return type:
bool
Sets this to represent the date, in the Gregorian calendar, with the given year
, month
and day
numbers. Returns true if the resulting date is valid, otherwise it sets this to represent an invalid date and returns false.
See also
- PySide6.QtCore.QDate.setDate(year, month, day, cal)
- Parameters:
year – int
month – int
day – int
cal –
PySide6.QtCore.QCalendar
- Return type:
bool
Sets this to represent the date, in the given calendar cal
, with the given year
, month
and day
numbers. Returns true if the resulting date is valid, otherwise it sets this to represent an invalid date and returns false.
See also
- PySide6.QtCore.QDate.startOfDay()#
- Return type:
This is an overloaded function.
- PySide6.QtCore.QDate.startOfDay(spec[, offsetSeconds=0])
- Parameters:
spec –
TimeSpec
offsetSeconds – int
- Return type:
This is an overloaded function.
Use startOfDay(const QTimeZone &)
instead.
Returns the start-moment of the day.
When a day starts depends on a how time is described: each day starts and ends earlier for those with higher offsets from UTC and later for those with lower offsets from UTC. The time representation to use can be specified either by a spec
and offsetSeconds
(ignored unless spec
is Qt::OffsetSeconds) or by a time zone.
Usually, the start of the day is midnight, 00:00: however, if a local time transition causes the given date to skip over that midnight (e.g. a DST spring-forward skipping over the first hour of the day day), the actual earliest time in the day is returned.
When spec
is OffsetFromUTC
, offsetSeconds
gives an implied zone’s offset from UTC. As UTC and such zones have no transitions, the start of the day is QTime
(0, 0) in these cases.
In the rare case of a date that was entirely skipped (this happens when a zone east of the international date-line switches to being west of it), the return shall be invalid. Passing TimeZone
as spec
(instead of passing a QTimeZone
) will also produce an invalid result, as shall dates that start outside the range representable by QDateTime
.
- PySide6.QtCore.QDate.startOfDay(zone)
- Parameters:
zone –
PySide6.QtCore.QTimeZone
- Return type:
Returns the start-moment of the day.
When a day starts depends on a how time is described: each day starts and ends earlier for those in time-zones further west and later for those in time-zones further east. The time representation to use can be specified by an optional time zone
. The default time representation is the system’s local time.
Usually, the start of the day is midnight, 00:00: however, if a time-zone transition causes the given date to skip over that midnight (e.g. a DST spring-forward skipping over the first hour of the day day), the actual earliest time in the day is returned. This can only arise when the time representation is a time-zone or local time.
When zone
has a timeSpec() of is OffsetFromUTC
or UTC
, the time representation has no transitions so the start of the day is QTime
(0, 0).
In the rare case of a date that was entirely skipped (this happens when a zone east of the international date-line switches to being west of it), the return shall be invalid. Passing an invalid time-zone as zone
will also produce an invalid result, as shall dates that start outside the range representable by QDateTime
.
See also
- PySide6.QtCore.QDate.toJulianDay()#
- Return type:
int
Converts the date to a Julian day.
See also
- PySide6.QtCore.QDate.toPython()#
- Return type:
object
- PySide6.QtCore.QDate.toString(format[, cal=QCalendar()])#
- Parameters:
format – str
cal –
PySide6.QtCore.QCalendar
- Return type:
str
- PySide6.QtCore.QDate.toString([format=Qt.TextDate])
- Parameters:
format –
DateFormat
- Return type:
str
This is an overloaded function.
Returns the date as a string. The format
parameter determines the format of the string.
If the format
is TextDate
, the string is formatted in the default way. The day and month names will be in English. An example of this formatting is “Sat May 20 1995”. For localized formatting, see toString()
.
If the format
is ISODate
, the string format corresponds to the ISO 8601 extended specification for representations of dates and times, taking the form yyyy-MM-dd, where yyyy is the year, MM is the month of the year (between 01 and 12), and dd is the day of the month between 01 and 31.
If the format
is RFC2822Date
, the string is formatted in an RFC 2822 compatible way. An example of this formatting is “20 May 1995”.
If the date is invalid, an empty string will be returned.
Warning
The ISODate
format is only valid for years in the range 0 to 9999.
See also
- PySide6.QtCore.QDate.toString(format[, cal=QCalendar()])
- Parameters:
format – str
cal –
PySide6.QtCore.QCalendar
- Return type:
str
- PySide6.QtCore.QDate.weekNumber()#
- Return type:
(week, yearNumber)
Returns the ISO 8601 week number (1 to 53).
Returns 0 if the date is invalid. Otherwise, returns the week number for the date. If yearNumber
is not None
(its default), stores the year as *``yearNumber``.
In accordance with ISO 8601, each week falls in the year to which most of its days belong, in the Gregorian calendar. As ISO 8601’s week starts on Monday, this is the year in which the week’s Thursday falls. Most years have 52 weeks, but some have 53.
Note
*``yearNumber`` is not always the same as year()
. For example, 1 January 2000 has week number 52 in the year 1999, and 31 December 2002 has week number 1 in the year 2003.
See also
- PySide6.QtCore.QDate.year()#
- Return type:
int
This is an overloaded function.
- PySide6.QtCore.QDate.year(cal)
- Parameters:
cal –
PySide6.QtCore.QCalendar
- Return type:
int
Returns the year of this date.
Uses cal
as calendar, if supplied, else the Gregorian calendar.
Returns 0 if the date is invalid. For some calendars, dates before their first year may all be invalid.
If using a calendar which has a year 0, check using isValid()
if the return is 0. Such calendars use negative year numbers in the obvious way, with year 1 preceded by year 0, in turn preceded by year -1 and so on.
Some calendars, despite having no year 0, have a conventional numbering of the years before their first year, counting backwards from 1. For example, in the proleptic Gregorian calendar, successive years before 1 CE (the first year) are identified as 1 BCE, 2 BCE, 3 BCE and so on. For such calendars, negative year numbers are used to indicate these years before year 1, with -1 indicating the year before 1.