change day by clicking on buttom

i want each time that im clickig on button that show me the Next day from day array list , can some one help me ?( the only way that i could get a answer is Math.random() to have difference result each time i am clicking on button , but i want that show me the next day each time i am clicking on it .

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<button onclick='day()'>Click to see</button>
<script>
    function day(){
       var days =['Monday','Thuesady','Wensday','Thursday','Friday','Saturday','Sunday']
        document.getElementById("demo").innerHTML = days[Math.floor(Math.random() *7)];} 
        
    }
</script>