A collection of methods around date/time values 更多...

#include <qwt_date.h>

Public 类型
enum	Week0Type { FirstThursday , FirstDay }
	How to identify the first week of year differs between countries 更多...

enum	IntervalType { Millisecond , Second , Minute , Hour , Day , Week , Month , Year }
	Classification of a time interval 更多...

enum	{ JulianDayForEpoch = 2440588 }

静态 Public 成员函数
static QDate	minDate ()
	Minimum for the supported date range

static QDate	maxDate ()
	Maximum for the supported date range

static QTimeZone	toTimeZone (Qt::TimeSpec timeSpec, int offsetSeconds=0)
	Convert a Qt::TimeSpec to a QTimeZone

static QDateTime	toDateTime (double value, Qt::TimeSpec=Qt::UTC)
	Translate from double to QDateTime

static QDateTime	toDateTime (double value, const QTimeZone &timeZone)
	Translate from double to QDateTime

static double	toDouble (const QDateTime &)
	Translate from QDateTime to double

static QDateTime	ceil (const QDateTime &, IntervalType)
	Ceil a datetime according the interval type

static QDateTime	floor (const QDateTime &, IntervalType)
	Floor a datetime according the interval type

static QDate	dateOfWeek0 (int year, Week0Type)
	Date of the first day of the first week for a year

static int	weekNumber (const QDate &, Week0Type)
	Find the week number of a date

static int	utcOffset (const QDateTime &)
	Offset in seconds from Coordinated Universal Time

static QString	toString (const QDateTime &, const QString &format, Week0Type)
	Translate a datetime into a string

详细描述

A collection of methods around date/time values

Qt offers convenient classes for dealing with date/time values, but Qwt uses coordinate systems that are based on doubles. QwtDate offers methods to translate from QDateTime to double and v.v.

A double is interpreted as the number of milliseconds since 1970-01-01T00:00:00 Universal Coordinated Time - also known as "The Epoch".

While the range of the Julian day in Qt4 is limited to [0, MAX_INT], Qt5 stores it as qint64 offering a huge range of valid dates. As the significance of a double is below this ( assuming a fraction of 52 bits ) the translation is not bijective with rounding errors for dates very far from Epoch. For a resolution of 1 ms those start to happen for dates above the year 144683.

An axis for a date/time interval is expected to be aligned and divided in time/date units like seconds, minutes, ... QwtDate offers several algorithms that are needed to calculate these axes.

参见: QwtDateScaleEngine, QwtDateScaleDraw, QDate, QTime

成员枚举类型说明

◆ anonymous enum

anonymous enum

枚举值
JulianDayForEpoch	The Julian day of "The Epoch"

◆ IntervalType

enum QwtDate::IntervalType

Classification of a time interval

Time intervals need to be classified to decide how to align and divide it.

枚举值
Millisecond	Millisecond
Second	Second
Minute	Minute
Hour	Hour
Day	Day
Week	Week
Month	Month
Year	Year

◆ Week0Type

enum QwtDate::Week0Type

How to identify the first week of year differs between countries

枚举值
FirstThursday	According to ISO 8601 the first week of a year is defined as "the week with the year's first Thursday in it". FirstThursday corresponds to the numbering that is implemented in QDate::weekNumber().
FirstDay	"The week with January 1 in it." In the U.S. this definition is more common than FirstThursday.

成员函数说明

◆ ceil()

QDateTime QwtDate::ceil	(	const QDateTime &	dateTime,
		IntervalType	intervalType
	)

static

Ceil a datetime according the interval type

参数

dateTime	Datetime value
intervalType	Interval type, how to ceil. F.e. when intervalType = QwtDate::Months, the result will be ceiled to the next beginning of a month

返回: Ceiled datetime

参见: floor()

◆ dateOfWeek0()

QDate QwtDate::dateOfWeek0	(	int	year,
		Week0Type	type
	)

static

Date of the first day of the first week for a year

The first day of a week depends on the current locale ( QLocale::firstDayOfWeek() ).

参数

year	Year
type	Option how to identify the first week

返回: First day of week 0

参见: QLocale::firstDayOfWeek(), weekNumber()

◆ floor()

QDateTime QwtDate::floor	(	const QDateTime &	dateTime,
		IntervalType	intervalType
	)

static

Floor a datetime according the interval type

参数

dateTime	Datetime value
intervalType	Interval type, how to floor. F.e. when intervalType = QwtDate::Months, the result will be floored to the beginning of a month

返回: Floored datetime

参见: ceil()

◆ maxDate()

QDate QwtDate::maxDate ( )

static

Maximum for the supported date range

The range of valid dates depends on how QDate stores the Julian day internally.

For Qt4 it is "Tue Jun 3 5874898"
For Qt5 it is "Tue Dec 31 2147483647"

返回: maximum of the date range

参见: minDate()

注解: The maximum differs between Qt4 and Qt5

◆ minDate()

QDate QwtDate::minDate ( )

static

Minimum for the supported date range

The range of valid dates depends on how QDate stores the Julian day internally.

For Qt4 it is "Tue Jan 2 -4713"
For Qt5 it is "Thu Jan 1 -2147483648"

返回: minimum of the date range

参见: maxDate()

◆ toDateTime() [1/2]

QDateTime QwtDate::toDateTime	(	double	value,
		const QTimeZone &	timeZone
	)

static

Translate from double to QDateTime

参数

value	Number of milliseconds since the epoch, 1970-01-01T00:00:00 UTC
timeZone	Time zone

返回: Datetime value

参见: toDouble(), QwtDate::toDateTime(double, Qt::TimeSpec)

◆ toDateTime() [2/2]

QDateTime QwtDate::toDateTime	(	double	value,
		Qt::TimeSpec	timeSpec = `Qt::UTC`
	)

static

Translate from double to QDateTime

参数

value	Number of milliseconds since the epoch, 1970-01-01T00:00:00 UTC
timeSpec	Time specification

返回: Datetime value

参见: toDouble(), QDateTime::setMSecsSinceEpoch()

注解: The return datetime for Qt::OffsetFromUTC will be Qt::UTC

◆ toDouble()

double QwtDate::toDouble ( const QDateTime & dateTime )

static

Translate from QDateTime to double

参数

dateTime Datetime value

返回: Number of milliseconds since 1970-01-01T00:00:00 UTC has passed.

参见: toDateTime(), QDateTime::toMSecsSinceEpoch()

警告: For values very far below or above 1970-01-01 UTC rounding errors will happen due to the limited significance of a double.

◆ toString()

QString QwtDate::toString	(	const QDateTime &	dateTime,
		const QString &	format,
		Week0Type	week0Type
	)

static

Translate a datetime into a string

Beside the format expressions documented in QDateTime::toString() the following expressions are supported:

w: week number ( 1 - 53 )
ww: week number with a leading zero ( 01 - 53 )

As week 1 usually starts in the previous year a special rule is applied for formats, where the year is expected to match the week number - even if the date belongs to the previous year.

参数

dateTime	Datetime value
format	Format string
week0Type	Specification of week 0

返回: Datetime string

参见: QDateTime::toString(), weekNumber(), QwtDateScaleDraw

◆ toTimeZone()

QTimeZone QwtDate::toTimeZone	(	Qt::TimeSpec	timeSpec,
		int	offsetSeconds = `0`
	)

static

Convert a Qt::TimeSpec to a QTimeZone

参数

timeSpec	Time specification
offsetSeconds	Offset in seconds (used for Qt::OffsetFromUTC)

返回: QTimeZone corresponding to the time specification

◆ utcOffset()

int QwtDate::utcOffset ( const QDateTime & dateTime )

static

Offset in seconds from Coordinated Universal Time

The offset depends on the time specification of dateTime:

Qt::UTC: 0, dateTime has no offset
Qt::OffsetFromUTC: returns dateTime.offsetFromUtc()
Qt::LocalTime: number of seconds from the UTC

For Qt::LocalTime the offset depends on the timezone and daylight savings.

参数

dateTime Datetime value

返回: Offset in seconds

◆ weekNumber()

int QwtDate::weekNumber	(	const QDate &	date,
		Week0Type	type
	)

static

Find the week number of a date

QwtDate::FirstThursday: Corresponding to ISO 8601 ( see QDate::weekNumber() ).
QwtDate::FirstDay: Number of weeks that have begun since dateOfWeek0().

参数

date	Date
type	Option how to identify the first week

返回: Week number, starting with 1

该类的文档由以下文件生成:

/home/runner/work/QWT/QWT/src/core/qwt_date.h
/home/runner/work/QWT/QWT/src/core/qwt_date.cpp

Public 类型

静态 Public 成员函数

详细描述

成员枚举类型说明

◆ anonymous enum

◆ IntervalType

◆ Week0Type

成员函数说明

◆ ceil()

◆ dateOfWeek0()

◆ floor()

◆ maxDate()

◆ minDate()

◆ toDateTime() [1/2]

◆ toDateTime() [2/2]

◆ toDouble()

◆ toString()

◆ toTimeZone()

◆ utcOffset()

◆ weekNumber()