My page:
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<apex:page controller="MonthYearpicklistcontroller">
  <apex:form >
  <apex:pageBlock >
  <apex:selectList size="1" value="{!myDateRange}">
     <apex:selectOptions value="{!DateRangeOptions}"/>
     <apex:actionSupport event="onchange" reRender="out1"/>
</apex:selectList>
<apex:commandButton value="Go" action="{!doAction}" />
<apex:pageBlockSection rendered="{!isBoolean}">
          <ul>
        <apex:outputLabel value="Account:">
        <apex:repeat value="{!accounts}" var="account">
       
            <li>
                {!account.Name}
               
                <ul>
                <apex:outputLabel value="Opportunity:">
                <apex:repeat value="{!account.children}" var="opportunity">
                    <li>
                        {!opportunity.Name}
                        
                        <ul>
                        <apex:outputLabel value="Contact:">
                        <apex:repeat value="{!opportunity.children}" var="contact">
                            <li>
                                {!contact.Name}
                            </li>
                        </apex:repeat>
                        </apex:outputLabel>
                        </ul>
                        
                    </li>
                </apex:repeat>
                </apex:outputLabel>
                </ul>
                
            </li>
        </apex:repeat>
        </apex:outputLabel>
        </ul>
       

</apex:pageBlockSection>
  </apex:pageBlock>
  </apex:form>
</apex:page>

My Controller:
----------------

public class MonthYearpicklistcontroller {
    public Boolean isBoolean { get; set; }
    public String myDateRange { get; set; }
   
    public List<SelectOption> getDateRangeOptions() {

        List<SelectOption> options = new List<SelectOption>();
        options.add(new SelectOption('1-2014','Jan-2014'));
        options.add(new SelectOption('2-2014','Feb-2014'));
        options.add(new SelectOption('3-2014','Mar-2014')); `enter code here`
        options.add(new SelectOption('4-2014','Apr-2014'));
        options.add(new SelectOption('5-2014','May-2014'));
        options.add(new SelectOption('6-2014','june-2014'));
        options.add(new SelectOption('7-2014','july-2014')); 
        options.add(new SelectOption('8-2014','Aug-2014'));
        options.add(new SelectOption('9-2014','Sep-2014'));
        options.add(new SelectOption('10-2014','Oct-2014'));
           return options; 
    }
     public List<Wrapper> accounts{
        get
        {
         
       
            List<Wrapper> accounts = new List<Wrapper>();
            List<Id> oppIds = new List<Id>();
            for(Account acc : [Select Id, Name, (Select Id, Name From Opportunities) From Account])
            {
                Wrapper account = new Wrapper();
                account.Id = acc.Id;
                account.Name = acc.Name;
                account.children = new List<Wrapper>();
                accounts.add(account);
                for(Opportunity opp : acc.Opportunities)
                {
                    Wrapper opportunity = new Wrapper();
                    opportunity.Id = opp.Id;
                    opportunity.Name = opp.Name;
                    opportunity.children = new List<Wrapper>();
                    account.children.add(opportunity);
                    oppIds.add(opp.Id);
                }
            }
            Map<Id, Opportunity> oppMap = new Map<Id, Opportunity>([Select Id, (Select Id, Contact.Name From OpportunityContactRoles) From Opportunity where id In :oppIds]);
            for(Wrapper account : accounts)
            {
                for(Wrapper opportunity : account.children)
                {
                    for(OpportunityContactRole opCR : oppMap.get(opportunity.Id).OpportunityContactRoles)
                    {
                        Wrapper contact = new Wrapper();
                        contact.Id = opCR.Id;
                        contact.Name = opCr.Contact.Name;
                        opportunity.children.add(contact);
                    }
                }
            }
            return accounts;
        }
    }
   
   
     public PageReference doAction() {
     isBoolean =true;
        return null;
    }
   
     public class Wrapper{
        public Id Id{get;set;}
        public String Name{get;set;}
        public List<Wrapper> children{get;set;}
    }

}

How to display based on picklist month and date related records?

please help me......