Calculating Daylight Saving Time

[Heckler]

Hey group,

Been working on code to universally determine if Daylight Saving Time is or is not in effect.
Would love a second set of eyes to make sure I have not missed anything or if there is a cleaner (less code) way of doing it.

I have used the following rules as a basis...

At present, daylight saving time in the United States
begins at 2:00 a.m. on the second Sunday of March and
ends at 2:00 a.m. on the first Sunday of November

below is a shot of a spread sheet that I made to try and account for all possibilities for when a given month (March and November) might begin.
Note 1:the seven colums across represent the seven possibilities for what day of the week the month may begin on.
Note 2: the numbers next to the letter for the day of the week represent the numberd day of the week (ie sun=1, mon=2... sat=7)



Here is my code...

'===========================================
'---  DST Calc (dec1 dow,dec2 mth,dec2 date)  ---
dstcalc:
dst = 1      'covers Apr, May, Jun, Jul, Aug, Sep, Oct
If (mth=1)  then dst = 0  'Jan
If (mth=2)  then dst = 0  'Feb
If (mth=12) then dst = 0  'Dec

March:
if mth=3 then                                       'March
    if  date <8 then
        dst=0
        elseif (date>7 and date<15) and dow=1 and hours<2 then
        dst=0 'Mar
        elseif (date=8  and dow>1) then
        dst=0
        elseif (date=9  and dow>2) then
        dst=0
        elseif (date=10 and dow>3) then
        dst=0
        elseif (date=11 and dow>4) then
        dst=0
        elseif (date=12 and dow>5) then
        dst=0
        elseif (date=13 and dow>6) then
        dst=0
    endif
endif

November:
if  (mth=11) then                                  'November                                      
    if  date >7 then
        dst=0
        elseif (date <8 and dow=1) and hours>1  then
        dst=0               
        elseif (date=2 and dow<3) then
        dst=0
        elseif (date=3 and dow<4) then
        dst=0
        elseif (date=4 and dow<5) then
        dst=0
        elseif (date=5 and dow<6) then
        dst=0
        elseif (date=6 and dow<7) then
        dst=0
    endif
endif
  
return

Note that the code assumes that DST is in effect (dst=1) and tries to find reasons that dst should be set to zero (dst=0)

your thoughts or ways to improve or simplify??

thanks