time.js

let t1 = 1433116798; // 2 seconds before midnight d1
let t2 = 1433116799; // 1 second before midnight d1
let t3 = 1433116801; // 1 seoncd after midnight d2
let t4 = 1433203201; // 1 second after midnight d3
const DAY_IN_SECONDS = 86400;

let days_since_epoch = t => { 
	return Math.floor( t / DAY_IN_SECONDS );
}

let days_span = ( start, end ) =>{ 
	return Math.abs( days_since_epoch( start ) - days_since_epoch( end ) ) + 1 
}

// 1
console.log( days_span( t1, t2 ) );
// 2
console.log( days_span( t1, t3 ) );
// 3
console.log( days_span( t1, t4 ) );