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phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2457

Posted: 11:45am 01 Mar 2025

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Just to clutter things up a bit more here is another one.
It doesn't use the Epoch() function but does use Day$() so no good for the MicroMite.

Function ds4.10(dateNow$)
'Determine Daylight Saving start and stop dates.
If dateNow$="" Then dateNow$=Date$
Local integer month=Val(Mid$(dateNow$,4,2)), days=Val(Left$(dateNow$,2)), n

If (month > 4) And (month < 10) Then ds4.10 = 0 'never DST in these months
If (month < 4) Or (month > 10) Then ds4.10 = 1 'always DST in these months
'Change all the 4s and 10s for DST stop/start months other than April and October
'Swap 0 and 1 in lines above for northern hemisphere

n=0 'If DST changes in second week change n to 8. If last week use the last day -7
If month = 4 Then 'End DST 1st Sunday in April
Do 'find the first Sunday
Inc n 'n = date of first Sunday
Loop Until Day$(Str$(n)+Right$(dateNow$,8)) = "Sunday"

If days < n Then 'compare date of first Sunday with supplied date
ds4.10 = 1
Else
ds4.10 = 0 'Swap 0 and 1 for northern hemisphere
EndIf
EndIf

n=0 'If DST changes in second week change n to 8. If last week use the last day -7
If month = 10 Then 'Start DST 1st Sunday in October
Do 'find the first Sunday
Inc n 'n = date of first Sunday
Loop Until Day$(Str$(n)+Right$(dateNow$,8)) = "Sunday"

If days < n Then 'compare date of first Sunday with supplied date
ds4.10 = 0
Else
ds4.10 = 1 'Swap 0 and 1 for northern hemisphere
EndIf
EndIf

End Function

Usage:-
> ? ds4.10() 'DST for current date
1
> ? ds4.10("07-04-2025") 'DST for any date
0
>
Edited 2025-03-02 07:29 by phil99

Footnote added 2025-03-02 14:25 by phil99
As this thread is going out in public (on FoTS) I thought I should comb my versions hair an give it a squirt of deodorant. Still not a good as Jim's last one (a few posts below) but can be readily configured for most DST rules and both hemispheres.

Function dst(dateNow$)
'Daylight Saving Time indicator
'output - dst() = 0 is standard time, dst = 1 is summer time
'change the values in the following four lines to suit local DST rules
Local integer hemi = 0 'northern hemisphere = 1, southern = 0
Local integer ChngMnth1 = 4, ChngMnth2 = 10 'Months when DST changes
Local integer ChngWeek1 = 5, ChngWeek2 = 5 'Week of the month for change, use 5 for the last week of the month
Local ChngDay$ = "Sunday" 'day of week for DST change. First letter upper case, rest lower case

If dateNow$="" Then dateNow$=Date$ 'if no date supplied use current date
'convert the 'change weeks' to start dates for finding the DST start/end days
ChngWeek1 = ChngWeek1 * 7 - 6
ChngWeek2 = ChngWeek2 * 7 - 6
If ChngWeek1 = 29 Then ChngWeek1 = 30 - 7 '<-Use 31 for a 31 day month if last week is used
If ChngWeek2 = 29 Then ChngWeek2 = 31 - 7 '<-Use 30 for a 30 day month if last week is used

Local integer month=Val(Mid$(dateNow$,4,2)), days=Val(Left$(dateNow$,2)), n=0

If (month > ChngMnth1) And (month < ChngMnth2) Then dst = 0 'no change in these months
If (month < ChngMnth1) Or (month > ChngMnth2) Then dst = 1 'no change in these months

If month = ChngMnth1 Then 'First change month
Do 'find the change day
Inc ChngWeek1 'day number for change, compare with supplied date
Loop Until Day$(Str$(ChngWeek1)+Right$(dateNow$,8))=ChngDay$ Or n>31

If days < ChngWeek1 Then 'set DST flag
dst = 1
Else
dst = 0
EndIf
EndIf

If month = ChngMnth2 Then 'Second change month
Do 'find the change day
Inc ChngWeek2 'day number for change4, compare with supplied date
Loop Until Day$(Str$(ChngWeek2)+Right$(dateNow$,8)) = ChngDay$ Or n>31

If days < ChngWeek2 Then 'set DST flag
dst = 0
Else
dst = 1
EndIf
EndIf

If hemi Then DST = Not DST 'adjust for hemisphere

End Function

'Test program to verify change dates.
Dim startdate$= "01-01-2024"
Dim startday, tdate$, m ,dstchange = 1
startday = Epoch(startdate$+" 00:00:00")/86400
For m = 0 To 3660*2
tdate$ = Left$(DateTime$((startday+m)*86400),10)
If dst(tdate$) <> dstchange Then
dstchange = dst(tdate$)
Print tdate$, Left$(Day$(tdate$),3), dst(tdate$)
EndIf
Next

Extended version of Jim's test program at the bottom.

Footnote added 2025-03-02 15:34 by phil99
Was testing DST change in the last week of the month when I posted the above so change:-
Local integer ChngWeek1 = 5, ChngWeek2 = 5 'Week of the month for change, use 5 for the last week of the month
to:-
Local integer ChngWeek1 = 1, ChngWeek2 = 1 'Week of the month for change, use 5 for the last week of the month
to return to the first week.

Footnote added 2025-03-03 06:56 by phil99
Extended testing shows an error in some years.
Here is the amended section of code.

If dateNow$="" Then dateNow$=Date$ 'if no date supplied use current date
'convert the 'change weeks' to start dates for finding the DST start/end days
ChngWeek1 = (ChngWeek1 - 1) * 7
ChngWeek2 = (ChngWeek2 - 1) * 7

palcal

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Joined: 12/10/2011
Location: Australia
Posts: 1970

Posted: 09:25pm 01 Mar 2025

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Maybe someone could put these in FOTS.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

disco4now

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Joined: 18/12/2014
Location: Australia
Posts: 983

Posted: 09:40pm 01 Mar 2025

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I have updated FotS and put a link to this discussion.

Latest F4 Latest H7 FotS

palcal

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Joined: 12/10/2011
Location: Australia
Posts: 1970

Posted: 11:09pm 01 Mar 2025

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@ TassyJim, what is this bit above the Function for

'
DIM startdate$= "01-01-2024"
DIM startday, tdate$,n,dstchange = 1

startday = EPOCH(startdate$+" 00:00:00")/86400
FOR n = 0 TO 3660
tdate$ = LEFT$(DATETIME$((startday+n)*86400),10)
IF dst(tdate$) <> dstchange THEN
dstchange = dst(tdate$)
PRINT tdate$
ENDIF
NEXT n

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6230

Posted: 12:46am 02 Mar 2025

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palcal said @ TassyJim, what is this bit above the Function for

That was just there to test for the next ~10 years.

Might come in handy if someone needs to edit the change dates to suit their country.
If I had done that first up, I would have found my initial error.

Jim
Edited 2025-03-02 10:47 by TassyJim

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TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6230

Posted: 02:34am 02 Mar 2025

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Last version.
Should be easy to adapt for all countries.

Not sure if US has cancelled DST yet.

' DST TassyJim March 2025
' test for 10 years
DIM startdate$= "01-01-2024"
DIM startday, tdate$,n,dstchange = 1

startday = EPOCH(startdate$+" 00:00:00")/86400
FOR n = 0 TO 3660
tdate$ = LEFT$(DATETIME$((startday+n)*86400),10)
IF dst(tdate$) <> dstchange THEN
dstchange = dst(tdate$)
PRINT tdate$,
IF dstchange THEN PRINT "Start" ELSE PRINT "Finish"
ENDIF
NEXT n
' end of test code

' DST starts month1 and week1, ends month2 and week2
' week = -1 for last Sunday in month
' week = 1 for first Sunday in month
' week = 2 for second Sunday in month
FUNCTION dst(testDate$)
LOCAL mth1start, mth2start, dst1, dst2, dst0, daynumnow
LOCAL month1 = 10, week1 = 1,month2 = 4, week2 = 1 ' australia
' local month1 = 9, week1 = -1,month2 = 4, week2 = 1 ' NZ
' local month1 = 3, week1 = -1,month2 = 10, week2 = -1 ' UK and EU
' local month1 = 3, week1 = 2, month2 = 11, week2 = 1 ' Canada, US?

IF week1 = -1 THEN month1 = month1 + 1 : week1 = 0
IF week2 = -1 THEN month2 = month2 + 1 : week2 = 0
week1 = week1 - 1
week2 = week2 - 1
IF testDate$ = "" THEN testDate$ = DATE$

daynumnow = EPOCH(testDate$+" 00:00:00")/86400
mth1start = EPOCH("01-"+STR$(month1,2,0,"0")+MID$(testDate$,6,5)+" 00:00:00")/86400
dst1 = (10-(mth1start MOD 7))MOD 7
dst1 = mth1start+dst1 +week1*7

mth2start = EPOCH("01-"+STR$(month2,2,0,"0")+MID$(testDate$,6,5)+" 00:00:00")/86400
dst2 = (10-(mth2start MOD 7))MOD 7
dst2 = mth2start+ dst2 +week2*7
IF dst1 > dst2 THEN dst0 = dst1 : dst1 = dst2 : dst2 = dst0
IF daynumnow < dst1 OR daynumnow >= dst2 THEN
dst = 1
ELSE
dst = 0
ENDIF
IF mth1start < mth2start THEN dst = 1 - dst
END FUNCTION

Jim

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palcal

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Joined: 12/10/2011
Location: Australia
Posts: 1970

Posted: 03:25am 02 Mar 2025

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@ TassyJim.... Thanks for these it is working well.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6230

Posted: 04:19am 02 Mar 2025

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Simplified the conditional statements.

' DST TassyJim March 2025
' test for 10 years
DIM startdate$= "01-01-2024"
DIM startday, tdate$,n,dstchange = 1

startday = EPOCH(startdate$+" 00:00:00")/86400
FOR n = 0 TO 3660
tdate$ = LEFT$(DATETIME$((startday+n)*86400),10)
IF dst(tdate$) <> dstchange THEN
dstchange = dst(tdate$)
PRINT tdate$,
IF dstchange THEN PRINT "Start" ELSE PRINT "Finish"
ENDIF
NEXT n
' end of test code

' DST starts month1 and week1, ends month2 and week2
' week = -1 for last Sunday in month
' week = 1 for first Sunday in month
' week = 2 for second Sunday in month
FUNCTION dst(testDate$)
LOCAL mth1start, mth2start, dst1, dst2, daynumnow
' Local month1 = 10, week1 = 1,month2 = 4, week2 = 1 ' Australia
' local month1 = 9, week1 = -1,month2 = 4, week2 = 1 ' NZ
' local month1 = 3, week1 = -1,month2 = 10, week2 = -1 ' UK and EU
LOCAL month1 = 3, week1 = 2, month2 = 11, week2 = 1 ' Canada, US?

IF week1 = -1 THEN month1 = month1 + 1 : week1 = 0 ' adjust for last sunday
IF week2 = -1 THEN month2 = month2 + 1 : week2 = 0
week1 = week1 - 1
week2 = week2 - 1
IF testDate$ = "" THEN testDate$ = DATE$

daynumnow = EPOCH(testDate$+" 00:00:00")/86400
mth1start = EPOCH("01-"+STR$(month1,2,0,"0")+MID$(testDate$,6,5)+" 00:00:00")/86400
dst1 = (10-(mth1start MOD 7))MOD 7
dst1 = mth1start+dst1 +week1*7

mth2start = EPOCH("01-"+STR$(month2,2,0,"0")+MID$(testDate$,6,5)+" 00:00:00")/86400
dst2 = (10-(mth2start MOD 7))MOD 7
dst2 = mth2start+ dst2 +week2*7

IF dst1 < dst2 AND daynumnow >= dst1 AND daynumnow < dst2 THEN
dst = 1
ELSEIF dst1 > dst2 AND (daynumnow >= dst1 OR daynumnow < dst2) THEN
dst = 1
ELSE
dst = 0
ENDIF
END FUNCTION

Jim

VK7JH
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