Yearly Hi/Lo channel problem

Hello all,

I'm trying to write up this indicator which will plot channels for the previous day/week/month and year. So far i have got the day/week/month all working but I am having some troubles with the yearly channel.

To do this for the previous 12 months doesn't seem too difficult but I would like to make the channel for the high/low of the past calander month (Jan-Dec) for all years in the chart history.

In it's present form it currently marks the high/low of the previous year but seems to be off by a month or two for some reason. Then after a couple of years the indi just runs flat.

Any ideas. Code Below:

#property strict
#property indicator_chart_window

#property indicator_buffers 8
#property indicator_color1 SkyBlue
#property indicator_color2 SkyBlue
#property indicator_color3 SeaGreen
#property indicator_color4 SeaGreen
#property indicator_color5 Coral
#property indicator_color6 Coral
#property indicator_color7 FireBrick
#property indicator_color8 FireBrick

int wkTFbars = 0, mnTFbars = 0;      //calculates the number of bars in a week for the current timeframe
int cur_day = 0, prev_day = 0, cur_year = 0, prev_year = 0, DAYshift = 0, WEEKshift = 0, MONTHshift = 0, cnt;
double DAYhigh[], DAYlow[], day_high = 0, day_low = 0, last_day_high = 0, last_day_low = 0;
double WEEKhigh[], WEEKlow[], week_high = 0, week_low = 0, last_week_high = 0, last_week_low = 0;
double MONTHhigh[], MONTHlow[], month_high = 0, month_low = 0, last_month_high = 0, last_month_low = 0;
double YEARhigh[], YEARlow[], year_low = 0, year_high = 0, last_year_high = 0, last_year_low;
//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int OnInit()
  {
//--- indicator buffers mapping
   IndicatorBuffers(6);
   IndicatorDigits(Digits);
   
   SetIndexBuffer (0, DAYhigh);
   SetIndexBuffer (1, DAYlow);
   SetIndexBuffer (2, WEEKhigh);
   SetIndexBuffer (3, WEEKlow);
   SetIndexBuffer (4, MONTHhigh);
   SetIndexBuffer (5, MONTHlow);
   SetIndexBuffer (6, YEARhigh);
   SetIndexBuffer (7, YEARlow);
   
   SetIndexStyle (0, DRAW_LINE,2);
   SetIndexStyle (1, DRAW_LINE,2);
   SetIndexStyle (2, DRAW_LINE,2);
   SetIndexStyle (3, DRAW_LINE,2);
   SetIndexStyle (4, DRAW_LINE,2);
   SetIndexStyle (5, DRAW_LINE,2);
   SetIndexStyle (6, DRAW_LINE,2);
   SetIndexStyle (7, DRAW_LINE,2);
   
   SetIndexDrawBegin(0,0);
   SetIndexDrawBegin(1,0);
   SetIndexDrawBegin(2,0);
   SetIndexDrawBegin(3,0);
   SetIndexDrawBegin(4,0);
   SetIndexDrawBegin(5,0);
   SetIndexDrawBegin(6,0);
   SetIndexDrawBegin(7,0);
   
   SetIndexLabel(0,"DAYhigh");
   SetIndexLabel(1,"DAYlow");
   SetIndexLabel(2,"WEEKhigh");
   SetIndexLabel(3,"WEEKlow");   
   SetIndexLabel(4,"MONTHhigh");
   SetIndexLabel(5,"MONTHlow");
   SetIndexLabel(6,"YEARhigh");
   SetIndexLabel(7,"YEARlow");
//---
   return(INIT_SUCCEEDED);
  }
//+------------------------------------------------------------------+
//| Custom indicator iteration function                              |
//+------------------------------------------------------------------+
int OnCalculate(const int rates_total,
                const int prev_calculated,
                const datetime &time[],
                const double &open[],
                const double &high[],
                const double &low[],
                const double &close[],
                const long &tick_volume[],
                const long &volume[],
                const int &spread[])
  {
//---
   for (cnt = Bars - 1; cnt >= 0 ;cnt--) {
   
      cur_day = TimeDay(Time[cnt]);
      cur_year = TimeYear(Time[cnt]);
   //Print("TFbars = ",TFbars);
      if (prev_day != cur_day) {
      
         DAYshift = iBarShift(Symbol(), PERIOD_D1, Time[cnt]);
         
         //Get the shift of the current Weeks bar
         WEEKshift = iBarShift(Symbol(), PERIOD_W1, Time[cnt]);
         
         //Get the shift of the current months bar
         MONTHshift = iBarShift(Symbol(), PERIOD_MN1, Time[cnt]);
         
         last_day_high = iHigh(Symbol(), PERIOD_D1, DAYshift + 1);
         last_day_low = iLow(Symbol(), PERIOD_D1, DAYshift + 1);
         
         last_week_high = iHigh(Symbol(), PERIOD_W1, WEEKshift + 1);
         last_week_low = iLow(Symbol(), PERIOD_W1, WEEKshift + 1);
         
         last_month_high = iHigh(Symbol(), PERIOD_MN1, MONTHshift + 1);
         last_month_low = iLow(Symbol(), PERIOD_MN1, MONTHshift +1);
          
         if (prev_year != cur_year) {
            last_year_high = iHigh(NULL, PERIOD_MN1, iHighest(NULL, PERIOD_MN1, MODE_HIGH, 12, MONTHshift)); 
            last_year_low = iLow(NULL, PERIOD_MN1, iLowest(NULL, PERIOD_MN1, MODE_LOW, 12, MONTHshift));
            
            prev_year = cur_year;
         } 
                    
         prev_day = cur_day;
      }
      
    /*  if (prev_year != cur_year) {
         last_year_high = iHigh(NULL, PERIOD_MN1, iHighest(NULL, PERIOD_MN1, MODE_HIGH, 12, Month())); 
         last_year_low = iLow(NULL, PERIOD_MN1, iLowest(NULL, PERIOD_MN1, MODE_LOW, 12, Month()));
            
         prev_year = cur_year;
      }*/
        
      
   day_high = last_day_high;
   day_low = last_day_low;   
      
   week_high = last_week_high;
   week_low = last_week_low;
   
   month_high = last_month_high;
   month_low = last_month_low;
   
   year_high = last_year_high;
   year_low = last_year_low;
   
   if (Period() == 1 || Period() == 5 || Period() == 15 || Period() == 30 || Period() == 60) {
      DAYhigh[cnt] = day_high;
      DAYlow[cnt] = day_low;
   }
   
   if (Period() == 1 || Period() == 5 || Period() == 15 || Period() == 30 || Period() == 60 || Period() == 240) {
         WEEKhigh[cnt] = week_high;
         WEEKlow[cnt] = week_low; 
   }
   
   if (Period() == 1 || Period() == 5 || Period() == 15 || Period() == 30 || Period() == 60 || Period() == 240 || 
       Period() == 1440) {
         MONTHhigh[cnt] = month_high;
         MONTHlow[cnt] = month_low;
   }
   
   YEARhigh[cnt] = year_high;
   YEARlow[cnt] = year_low;
      
   }
//--- return value of prev_calculated for next call
   return(rates_total);
  }
//+------------------------------------------------------------------+