Determine whether a user is in the northern or southern hemisphere

[c.haslam]

My PC is in the northern hemisphere. My script needs to know whether another PC running my script is in the northern or southern hemisphere.

This is needed to determine if Daylight time is in effect from April to November or from November to April.

Edited September 28 by c.haslam

[jchd]

This information has nothing to do with hemispheres!

_Date_Time_GetTimeZoneInformation() is your friend.

[c.haslam]

$ar = _Date_Time_GetTimeZoneInformation($ar) on my PC is returning, today: $ar[0]=2, $ar[1]=300, $ar[2]="Eastern Standard Time", $ar[4]=0, $ar[5] = "Eastern Daylight Time", $ar[7]=-60 . ($ar[3] and $ar[6] are structs.)

My PC (and I) are on EDT until 2 AM on first Sunday of November. We are indeed now 5 hours (300 minutes) behind UCT (GMT).

I am using TaskScheduler.au3. It requires that the start and end boundaries, for _TS_Wrapper_TriggerLogon(), be in the format YYYY-MM-DDTHH:MM:SS(+-)HH:MM i.e. time in UCT + or -  bias. Example: 2024-09-28T14:20:55-05:00

Let's say that the user wants to set a trigger today, in local time, on 2024-12-14  at 14:20:25. My script has to convert it to the required format.

In the northern hemisphere while we are on Daylight time now, on 2024-12-14 my PC will be on Standard time, so the bias will then be -04:00 . But  a user in the southern hemisphere will be on Daylight time because his Daylight time runs from November to April, so for a user in a country in the southern hemisphere his bias would decrease

So the hemisphere matters.

A question: when my PC changes to Standard time on November 3, what will $ar[1] , $ar[2] and $ar[7] be ?  I find descriptions in the help for return value confusing.

A user can enter any date he wishes. Hd enters it in local time, not UCT.

Of course, _Date_Time_GetTimeZoneInformation() get the current information, not the information for a future date.

Edited September 29 by c.haslam

[argumentum]

..and, what if that country does not follow daylight time ? ( Iran, Jordan, Namibia, Russia, Samoa, Syria, Turkey, Uruguay, Mexico  )
What then ? What if that changes after your software is done ?

What if a user wants to wake up at 7:00, will UTC have anything to do with local time ?

Is always 5 in the afternoon somewhere. I'll go for a drink now  

[c.haslam]

My script does handle Daylight time not being used. In this case, the 0th element returned by _Date_Time_GetTimeZoneInformation() is zero.

BTW TaskScheduler.au3 provides access to Windows' Task Scheduler.

Windows has the same format: see https://learn.microsoft.com/en-us/windows/win32/taskschd/trigger-startboundary

[jchd]

DST has nothing to do with North, South, East or West. DST is decided by the rules in force in the country/region/city and the timestamp you consider.

7 hours ago, c.haslam said:

($ar[3] and $ar[6] are structs.)

This where DST details are available.

 

7 hours ago, c.haslam said:

time in UCT + or -  bias. Example: 2024-09-28T14:20:55-05:00

This timestamp format is not UTC, it is local time. The last part (-05:00) indicates the shift from/to UTC. You must subtract this value to get UTC.

This exemple is = 2024-09-28 19:20:55Z

[Somerset]

@c.haslamAsking the user a question is out right impossible?

gps device?

water spin query?

celestial observation question?

[jchd]

1 hour ago, Somerset said:

water spin query?

That is urban legend. Coriolis force is way too weak to impact water in a sink.

[c.haslam]

Quoting Microsoft:

 "For example the date October 11th, 2005 at 1:21:17 in the Pacific Time zone would be written as 2005-10-11T13:21:17-08:00"

Assume this is a startBoundary for a trigger.

On a PC in Vancouver, the user's task would trigger when the Windows desktop clock shows 1:21 PM, October 11 being in Standard time.

But consider 2005-08-11T13:21:17T-08:00. The user' task would trigger on August 11th, 2005 when the Windows desktop clock shows 12:21 PM !

For the task to trigger when the Windows desktop clock 1:21 PM  when Daylight time is in effect, the parameter needs to be 2005-08-11T13:21:17T-09:00

So Standard vs. Daylight matters.

Edited September 29 by c.haslam

[c.haslam]

My current northern hemisphere code is below. It has not been tested.

expandcollapse popup

Func FormatBoundaryForTS_NorthernHemisphere($LocalDateTime)

    Local $ar = _Date_Time_GetTimeZoneInformation()
    Local $biasMins

    If $ar[0]=0 Then
        $biasMins = - $ar[1]
    Else
; The Help is not clear to me: On my PC on 2024-09-25, on daylight time, $ar[0] is 2, $ar[1] is 300, $ar[4] is 0 and $ar[7] is -60
        Local $vec = StringSplit($LocalDateTime,"/ :")
        Local $yr = $vec[1], $mon = $vec[2], $day = $vec[3]
        Local $bSummer

        Switch ($mon)   ; Summer (DayLight Saving) from 2nd Sunday in Apr to day before 2nd Sunday in Nov
            Case 3  ; Mar
                Local $q = 0
                For $i = 1 to 30
                    if _DateToDayOfWeek($yr,3,$i) = 1 Then  ; Sunday
                        $q += 1
                        if $q=2 Then
                            ExitLoop
                        EndIf
                    EndIf
                Next
                $bSummer = $day >= $i
            Case 11 ; Nov
                For $i = 1 to 30
                    if _DateToDayOfWeek($yr, 11, $i) = 1 Then
                        ExitLoop
                    EndIf
                Next
                $bSummer = $day < $i
            Case 4 to 10
                $bSummer = True
            Case Else
                $bSummer = False
        EndSwitch

        If $bSummer Then
            $biasMins = - $ar[1]    ; Eastern: $biasMins = -300 (-5 hours)
        Else
            $biasMins = -($ar[1] + $ar[7])  ; Eastern: $biasMins = -300 + 50 (-4 hours)
        EndIf
    EndIf

    Local $ret
    $ret = _DateAdd("n",$biasMins,$LocalDateTime)
    $ret = StringReplace($ret,"/","-")
    $ret = StringReplace($ret," ","T")
    if $biasMins>0 Then
        $ret &= "-"
    Else
        $ret &= "+"
    EndIf
    Local $hours = Int($biasMins/60)
    Local $mins = Mod($ret,60)
    Local $t = StringRegExp("%02d:%02d",$hours,$mins)
    $ret &= $t

    Return $ret
EndFunc

 

[Dan_555]

deleting this

Edited October 1 by Dan_555
deleting

[argumentum]

1 hour ago, c.haslam said:

"For example the date October 11th, 2005 at 1:21:17 in the Pacific Time zone would be written as 2005-10-11T13:21:17-08:00"

Then don't. Don't add the "-08:00"
From the example "StartBoundary (triggerBaseType) Element"

<BootTrigger>
    <StartBoundary>2005-01-01T08:00:00</StartBoundary>
    <EndBounadry>2007-01-01T08:00:00</EndBoundary>
    <Enabled>true</Enabled>
    <Repetition></Repetition>
    <ExecutionTimeLimit></ExecutionTimeLimit>
    <Delay><Delay>
 </BootTrigger>

 

[jchd]

I never used the TaskScheduler.au3 UDF but it should store event datetime stamps in UTC, without any offset. The task should trigger when the PC UTC clock matches that of the scheduler, period. Exactly like what @argumentum posted while I was typing.

UTC is the same for everyone everywhere on Earth and anytime.

Of course if you move your laptop from one timezone + DST rule to another area having another set of rules, without telling your PC that the local rules have changed, then the bell will ring at the wrong time.

Contrary to a laptop, a smartphone connected to a local GSM network knows when you change location and hopefully adjusts the local parameters to where you go.

[argumentum]

...reading stuff..., the technical writer will take you to the exquisite scenarios that their code can do !, and that can confuse the reader as if that is the only practical way to get something done.
Our own UDFs have the _funcWhatever() and the _funcWhateverEx() where the Ex version is quite impractical but there, as it is more powerful but generally, uselessly cumbersome to use. Hence the non-Ex version.

In this case, where the time zone can be included, the technical writer presents a situation to justify it's existence. But does not make a case that is not a necessity   

[Somerset]

The  OP could go through ip location web site. <-regretting thinking of it.

Edited September 29 by Somerset

[jchd]

That's not reliable (VPN or ISP not under exact same rules) nor enough. Even a GPS location doesn't tell you which rules are in force, even less which rules to use elsewhere in some future.

Look at how fast all those things change: https://time.is/fr/time_zone_news

 

[c.haslam]

argumentum's post re (+-)HH;MM is interesting. I wonder, if one omits (+-)HH;MM, whether the startBoundary is in UTC or in local datetime. It is surprising that Microsoft do not state that (+-)HH:MM is optional.

jchd wrote: "it should store event datetime stamps in UTC, without any offset".

If this is the case, I still have a problem.

My script is an appointment reminder. Through a GUI, the user enters a date and time plus a message. The script creates a task.  At the datetime, the task runs, running AutoIt code that creates a msgBox. 

An example for a user on Eastern Daylight time assuming that startBoundary without (+-)HH:MM is in local time: 

• User enters 2024-12-01 09:00 and "It's time to go".
• The script creates a task with  startBoundary 2024-12-01T09:00
• At 2024-12-01 09:00 local, the task runs if startBoundary is in local time
• The user sees a msgBox. 

But if the startBoundary is UCT the task would run at 05:00, long before he awakes.

Experimentation shows that without (+-)HH:MM startBoundary is in UCT.

To handle startBoundary being in UCT, the difference between Daylight and UCT is required. There are 2 ways, with $udt = "2024/12/01 09:00"

Way 1

$udt = StringReplace($udt, "/", "-")
$edt = StrinhReplace($udt," " , "T")
$$tartBoundary = $udt & "-04:00"

Way 2

$dt = _DateAdd(-4, "h", $udt)
$udt = StringReplace($dt,"/", "-")
$startBoundary = StringReplace($dt," ", "T")

Both should work. Both require the time zone.

I accept that my script will only work for users in countries that:

• do not have Daylight time
• have Daylight time from the third Sunday in April to the first Sunday in November.

Edited September 30 by c.haslam

[argumentum]

I'd guess that if the UTC marker is not there, local time is used. Try it on your PC ( some event 2 minutes in the future ) and let us know.

Edit: unless you reside in Greenwich  

Edited September 30 by argumentum
fun

[jchd]

There is no such thing as an UTC marker!

The letter Z sometimes found at the end of a timestamp means "Zulu", for Zero. The time before is both UTC and local in timezone +0 (they are equal).

BTW, Greenwich is to be forgotten, speaking of time. GMT has no more any reasonable meaning since 1972-01-01. Use UTC instead.

[c.haslam]

Running this script shows that without (+-)HH:MM, $startTime and $endTime are in local time:

#include "TaskScheduler.au3"

Local $oService = _TS_Open()
Local $startTime = _DateAdd("n",3,_NowCalc())
$startTime = StringReplace($startTime,"/","-")
$startTime = StringReplace($startTime," ","T")
Local $endTime = _DateAdd("n",20,_NowCalc())
$endTime = StringReplace($endTime,"/","-")
$endTime = StringReplace($endTime," ","T")

Local $oTaskDefinition = _TS_Wrapper_TaskCreate($oService, "", "")
_TS_Wrapper_PrincipalSet($oTaskDefinition,$TASK_LOGON_INTERACTIVE_TOKEN)
_TS_Wrapper_TriggerDateTime($oTaskDefinition,$TASK_TRIGGER_TIME,0, 0, $startTime,$endTime)
_TS_Wrapper_ActionCreate($oTaskDefinition,"Notepad")
if _TS_FolderExists($oService,"\Test")=0 Then
    _TS_FolderCreate($oService,"\Test")
EndIf
_TS_Wrapper_TaskRegister($oService, "\Test","starttime",$oTaskDefinition, Default, Default,$TASK_LOGON_INTERACTIVE_TOKEN)
 MsgBox(1,30,"$startTime " & $startTime & " $endTime " & $endTime)
_TS_Close($oService)

Microsoft should say this.

I was confused by $TASK_LOGON_INTERACTIVE_TOKEN. It means when the user is logged on. As MS says: "User must already be logged on. The task will be run only in an existing interactive session"

Causing a task to run soon after logging on appears to depend on the Delay parameter being set. Such a task also needs $TASK_LOGON_INTERACTIVE_TOKEN.

BTW when the task has run, the task continues to exist but has Next Run Time as N/A in schtasks /query and no value in _TS_TaskList(). When the task has run, call _TS_TaskDelete() to delete it after Notepad opens.

Edited October 1 by c.haslam
Added "to delete it after Notepad opens"