<lightning:buttonMenu alternativeText="Toggle menu" iconSize="x-Small" onselect="{!c.handleMenuSelect}">

 <a><lightning:icon aura:id="icon1" class="icon_chat" size="small" iconName='utility:chat' /></a>

 if(string.isBlank(searchKey)){
            lstOfGroup =  [select Id,Name,CreatedDate from Group where Id IN: lstOfGroupIds ORDER BY NAME ASC LIMIT 500];
            system.debug('GroupNames>>' + lstOfGroup);
            }

This "CreatedDate" should be in "dd-mm-yyy" format..

<lightning:button class="slds-button" variant="base" value="{!usr.UserId}" label="{!usr.Username}" onclick="{!c.openuserqueue}" />

 if(string.isBlank(searchKey)){
            lstOfGroup =  [select Id,Name,CreatedDate from Group where Id IN: lstOfGroupIds ORDER BY NAME ASC LIMIT 500];
            system.debug('GroupNames>>' + lstOfGroup);
            }

This "CreatedDate" should be in "dd-mm-yyy" format..

<lightning:button class="slds-button" variant="base" value="{!usr.UserId}" label="{!usr.Username}" onclick="{!c.openuserqueue}" />