' IsDst() uses global date$ and time$ to determine if today is daylight savings.
' The algorithm uses the european transition at last sunday in March and October at 02:00 am
' Volhout

Print IsDst()

End

Function IsDst()
 'uses time$ and date$
 Local m,o,md,od,d,y,dd$

 'this is today, this hour
 d=Epoch(Date$+" "+Time$)

 y=Val(Right$(Date$,4))

 'start of dst on last sunday in March in current year at 02:00
 md=31-dow%(y,3,31) 'March has 31 days
 dd$=Str$(md,2,0)+"-03-"+Str$(y)
 m=Epoch(dd$+" 02:00:00")

 'end of dst on last sunday in October in current year at 02:00
 od=31-dow%(y,10,31) 'October has 31 days
 dd$=Str$(od,2,0)+"-10-"+Str$(y)
 o=Epoch(dd$+" 02:00:00")

 IsDst = (m<d) And (o>d)
End Function


Function dow%(y,m,d)       'day of week
 'returns day of the week (0 sunday .. 6 saturday)
 Local t%(11)=(0,3,2,5,0,3,5,1,4,6,2,4)
 If m<3 Then y=y-1
 dow%=(y+y\4-y\100+y\400+t%(m-1)+d) Mod 7
End Function