JSFiddle - React, Tailwind, and code Playground

JavaScript

function timeDiff(current, previous) {
        
        var msPerMin = 60 * 1000;
        var msPerHr = msPerMin * 60;
        var msPerDay = msPerHr * 24;
        var msPerMonth = msPerDay * 30;
        var msPerYear = msPerDay * 365;
        
        var elapsed = current - previous;
        
        if (elapsed < msPerMin) {
             return Math.round(elapsed / 1000) + ' seconds ago';   
        }
        
        else if (elapsed < msPerHr) {
             return Math.round(elapsed / msPerMin) + ' minutes ago';   
        }
        
        else if (elapsed < msPerDay ) {
             return Math.round(elapsed / msPerHr ) + ' hours ago';   
        }
      
        else if (elapsed < msPerMonth) {
            return 'approximately ' + Math.round(elapsed / msPerDay) + ' days ago';   
        }
    
        else if (elapsed < msPerYear) {
            return 'approximately ' + Math.round(elapsed / msPerMonth) + ' months ago';   
        }
    
        else {
            return 'approximately ' + Math.round(elapsed / msPerYear ) + ' years ago';   
        }
    }



var now = new Date();
var someDate = new Date(2011, 04, 24, 12, 30, 00, 00);
alert(timeDiff(now, someDate));