설정된 시간 간격으로 볼 수있는 콘텐츠가 변경되지만 나중에 이전 콘텐츠가 깜박입니다.

$( document ).ready(function() {  
    SetImage();
    window.setInterval(SetImage,1000);
});

function SetImage(){     
    var nowdate = new Date() ;
    
    var waketime = new Date();     
    waketime.setHours(6);
    waketime.setMinutes(30);
    
    var bedtime = new Date();     
    bedtime.setHours(12);
    bedtime.setMinutes(00);
    
    if(waketime < nowdate  && nowdate < bedtime){
         $('.day').show();
         $('.night').hide();
    }else{
         $('.night').show();
         $('.day').hide();
    }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="col content">
	<img class="day" src="images/img05.jpg"/>
	<img class="night" src="images/img07.jpg"/>
</div>
<div class="col sidebar">
	<img class="day" src="images/img06.jpg"/>
	<img class="night" src="images/img08.jpg"/>
</div>