TimeZoneRule Class Reference

#include <timezonerule.h>

Public Member Functions
	TimeZoneRule ()
	TimeZoneRule (const QString &smonth, const QString &sday, const QTime &stime, const QString &rmonth, const QString &rday, const QTime &rtime, const double &offset=1.00)
double	deltaTZ () const
bool	equals (TimeZoneRule *r)
bool	isDSTActive (const KStarsDateTime &date)
bool	isEmptyRule ()
KStarsDateTime	nextDSTChange ()
KStarsDateTime	nextDSTChange_LTime ()
void	reset_with_ltime (KStarsDateTime &ltime, const double TZoffset, const bool time_runs_forward, const bool automaticDSTchange=false)
void	setDST (bool activate=true)

Detailed Description

This class provides the information needed to determine whether Daylight Savings Time (DST; a.k.a.

"Summer Time") is currently active at a given location. There are (at least) 25 different "rules" which govern DST around the world; a string identifying the appropriate rule is attachded to each city in Cities.dat.

The rules themselves are stored in the TZrulebook.dat file, which is read on startup; each line in the file creates a TimeZoneRule object.

TimeZoneRule consists of QStrings identifying the months and days on which DST starts and ends, QTime objects identifying the time at which the changes occur, and a double indicating the size of the offset in hours (probably always 1.00).

Month names should be the English three-letter abbreviation, uncapitalized. Day names are either an integer indicating the calendar date (i.e., "15" is the fifteenth of the month), or a number paired with a three-letter abbreviation for a weekday. This indicates the Nth weekday of the month (i.e., "2sun" is the second Sunday of the Month). Finally, the weekday string on its own indicates the last weekday of the month (i.e., "mon" is the last Monday of the month).

The isDSTActive(KStarsDateTime) function returns true if DST is active for the DateTime given as an argument.

The nextDSTChange(KStarsDateTime) function returns the KStarsDateTime of the moment at which the next DST change will occur for the current location.

Author

Jason Harris

Version

1.0

Definition at line 56 of file timezonerule.h.

Constructor & Destructor Documentation

TimeZoneRule::TimeZoneRule

(

)

Default Constructor.

Makes the "empty" time zone rule (i.e., no DST correction)

Definition at line 25 of file timezonerule.cpp.

TimeZoneRule::TimeZoneRule	(	const QString &	smonth,
		const QString &	sday,
		const QTime &	stime,
		const QString &	rmonth,
		const QString &	rday,
		const QTime &	rtime,
		const double &	offset = 1.00
	)

Constructor.

Create a TZ rule according to the arguments.

Parameters

smonth	the three-letter code for the month in which DST starts
sday	a string encoding the day on which DST starts (see the class description)
stime	the time at which DST starts
rmonth	the three-letter code for the month in which DST reverts
rday	a string encoding the day on which DST reverts (see the class description)
rtime	the time at which DST reverts
offset	the offset between normal time and DS time (always 1.00?)

Definition at line 29 of file timezonerule.cpp.

Member Function Documentation

double TimeZoneRule::deltaTZ ( ) const

inline

Returns

the current Timezone offset, compared to the timezone's Standard Time. This is typically 0.0 if DST is inactive, and 1.0 if DST is active.

Definition at line 88 of file timezonerule.h.

bool TimeZoneRule::equals

(

TimeZoneRule *

r

)

Returns

true if this rule is the same as the argument.

Parameters

r	the rule to check for equivalence

Definition at line 406 of file timezonerule.cpp.

bool TimeZoneRule::isDSTActive

(

const KStarsDateTime &

date

)

Determine whether DST is in effect for the given DateTime, according to this rule.

Parameters

date	the date/time to test for DST

Definition at line 179 of file timezonerule.cpp.

bool TimeZoneRule::isEmptyRule ( )

inline

Returns

true if the rule is the "empty" TZ rule.

Definition at line 79 of file timezonerule.h.

KStarsDateTime TimeZoneRule::nextDSTChange ( )

inline

Returns

computed value for next DST change in universal time.

Definition at line 103 of file timezonerule.h.

KStarsDateTime TimeZoneRule::nextDSTChange_LTime ( )

inline

Returns

computed value for next DST change in local time.

Definition at line 106 of file timezonerule.h.

void TimeZoneRule::reset_with_ltime	(	KStarsDateTime &	ltime,
		const double	TZoffset,
		const bool	time_runs_forward,
		const bool	automaticDSTchange = false
	)

Recalculate next dst change and if DST is active by a given local time with timezone offset and time direction.

Parameters

ltime	the time to be tested
time_runs_forward	time direction
TZoffset	offset of timezone in some fictional unit
automaticDSTchange	is automatic DST change?

Todo:

Check dox for TZoffset

There are some problems using local time for getting next daylight saving change time.

1. The local time is the start time of DST change. So the local time doesn't exists and must corrected.
2. The local time is the revert time. So the local time exists twice.
3. Neither start time nor revert time. There is no problem.

Problem #1 is more complicated and we have to change the local time by reference. Problem #2 we just have to reset status of DST.

automaticDSTchange should only set to true if DST status changed due to running automatically over a DST change time. If local time will changed manually the automaticDSTchange should always set to false, to hold current DST status if possible (just on start and revert time possible).

Definition at line 301 of file timezonerule.cpp.

void TimeZoneRule::setDST

(

bool

activate = true

)

Toggle DST on/off.

The activate argument should probably be isDSTActive()

Parameters

activate

if true, then set DST active; otherwise, deactivate DST

Definition at line 63 of file timezonerule.cpp.

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The documentation for this class was generated from the following files:

• timezonerule.h
• timezonerule.cpp