Vue Js calculate time left to given date

<!DOCTYPE html>
<html lang="en">
<head>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
    <div id="app">
        <h3>Vue Js calculate time left to given date</h3>
        <div class="countdown">
            <div>
                <span class="days">{{ days }}</span>
                <div class="smalltext">Days</div>
            </div>
            <div>
                <span class="hours">{{ hours }}</span>
                <div class="smalltext">Hours</div>
            </div>
            <div>
                <span class="minutes">{{ minutes }}</span>
                <div class="smalltext">Minutes</div>
            </div>
            <div>
                <span class="seconds">{{ seconds }}</span>
                <div class="smalltext">Seconds</div>
            </div>
        </div>
    </div>

this.days = Math.floor(timeDifference / (1000 * 60 * 60 * 24));
                    this.hours = Math.floor((timeDifference / (1000 * 60 * 60)) % 24);
                    this.minutes = Math.floor((timeDifference / 1000 / 60) % 60);
                    this.seconds = Math.floor((timeDifference / 1000) % 60);
                }
            }
        })
    </script>
    <style scoped>
        #app {
            font-family: Arial, sans-serif;
            text-align: center;
            margin: 50px auto;
            max-width: 400px;
        }

h3 {
            font-size: 32px;
            font-weight: bold;
            margin-bottom: 20px;
            color: #333;
        }

.countdown {
            display: flex;
            justify-content: space-between;
            align-items: center;
            border: 2px solid #ccc;
            border-radius: 5px;
            padding: 20px;
        }

.countdown div {
            display: flex;
            flex-direction: column;
            align-items: center;
        }

.countdown div span {
            font-size: 48px;
            font-weight: bold;
            color: #333;
        }

.countdown div .smalltext {
            font-size: 16px;
            text-transform: uppercase;
            color: #777;
            margin-top: 5px;
        }
    </style>
</body>

</html>