$regfile = "m8def.dat"                                   ' specify the used micro
$hwstack = 32                                               ' default use 32 for the hardware stack
$swstack = 10                                               ' default use 10 for the SW stack
$framesize = 40                                             ' default use 40 for the frame space

$crystal = 4000000                                         ' used crystal frequency
$baud = 19200                                               ' use baud rate


Enable Interrupts

Config Clock = Soft
Config Date = YMD , Separator =.' ANSI-Format

dim dateArr(6) As Byte
dim gd as byte, b as byte
dim wday as byte, repetition as byte, month as byte, year as byte, Strweekday as string * 10

declare Function repetition_of_day( byval wday as byte, byval repetition as byte, byval month as byte, byval year as byte) as byte

$sim

'main


for b = 1 to 12
' Get Day from 3rd repetition from JAN to DEC 2019
' in case result is "0", it is no valid Result!
  wday = 6        ' 0-6  0=Monday
  repetition = 3  ' nth repetition of Day
  month = b
  year = 19
  gd = repetition_of_day( wday, repetition, month, year)
  if gd > 0 then
    Strweekday = Lookupstr(wday , Weekdays)
    print "Search: repetition #";str(repetition);" of ";Strweekday;" in ";str(month);"-20";str(year);" is ";str(gd);"-";str(month);"-20";str(year)
  else
    print "Search: repetition #";str(repetition);" of ";Strweekday;" in ";str(month);"-20";str(year);" is not in month Range"
  end if
next


end
'end of main
' Search: repetition #3 of Tuesday in 12-2019 is 17-12-2019
' Search: repetition #3 of Thursday in 11-2019 is 21-11-2019




Function repetition_of_day( byval wday as byte, byval repetition as byte, byval month as byte, byval year as byte) as byte
' wday = 0 to 6, Monday starts with 0
' repetition = nth repetition of Weekday "wday"
local fwom as byte, ldom as byte, hb as byte, foow as byte, Lsyssec As Long


  dateArr(1) = 0     'sec
  dateArr(2) = 0     'min
  dateArr(3) = 1     'hour
  dateArr(4) = 1     'day
  dateArr(5) = month 'month
  dateArr(6) = year  'year
  ' get first Weekday of month
  Lsyssec = Syssec(dateArr(1))
  fwom = DayOfWeek(lsyssec)

  ' getting last day of month
  ' 1) get first day from following month
  if month = 12 then
     dateArr(5)=1
     incr dateArr(6)
  else
     incr dateArr(5)
  end if
  Lsyssec = Syssec(dateArr(1))
  ' 2) substract one Day, so we've last day in month
  Lsyssec=Lsyssec-86400
  dateArr(4)=Date(Lsyssec)
  ' 3) get last Day of Month
  ldom=dateArr(4)

  ' calculate Day of first occurence of wday (foow) in month
  if fwom <= wday then
    foow = wday - fwom
    incr foow
  else
    foow = wday + 7
    foow = foow - fwom
    incr foow
  end if


  ' now "foow" holds the first Weekday we're searching for as Day in Month in given month and year

  ' we've to check if the nth "repetition" of our Weekday is in Range of month!
  decr repetition
  hb = repetition * 7
  hb=hb+foow
  if hb <= ldom then
    ' it's ok! we're inside the month Range
    repetition_of_day = hb
  else
    ' we're outside the day-Range of Month
    repetition_of_day = 0
  end if
end function



Weekdays:

Data "Monday" , "Tuesday" , "Wednesday" , "Thursday" , "Friday" , "Saturday" , "Sunday"
 

  wday = 6        ' 0-6  0=Monday
  repetition = 1  ' nth repetition of Day
  month = 12
  year = 19

print "Search: repetition #"+str(repetition)+" of "+Strweekday+" in "+str(month)+"-20"+str(year)+" is not in month Range"

print "Search: repetition #"; repetition; " of "; Strweekday; " in ";month; "-20"; year;" is not in month Range"

Strweekday = Lookupstr(wday , Weekdays)