CSS Zeitleiste (Timeline) mit CSS & HTML für HTML-Seite oder HTML-Box

/* Timeline */
.timeline {
    position: relative;
    max-width: 800px;
    margin: 40px auto;
    padding-left: 30px;
    border-left: 3px solid #4a6cf7;
    font-family: Arial, sans-serif;
}

.timeline-item {
    position: relative;
    margin-bottom: 40px;
}

.timeline-item::before {
    content: "";
    position: absolute;
    left: -11px;
    top: 5px;
    width: 16px;
    height: 16px;
    background: #135183;
    border-radius: 50%;
}

.timeline-date {
    font-weight: bold;
    color: #135183;
    margin-bottom: 5px;
}

.timeline-content {

    padding: 15px 20px;
    border-radius: 6px;
}

.timeline-content h3 {
    margin-top: 0;
    font-size: 18px;

<div class="timeline">
    <div class="timeline-item">
        <div class="timeline-date">Zeitpunkt A</div>
        <div class="timeline-content">
            <h3>Ereignis A</h3>
                   </div>
    </div>

    <div class="timeline-item">
        <div class="timeline-date">Zeitpunkt B</div>
        <div class="timeline-content">
            <h3>Ereignis B</h3>
         
        </div>
    </div>

    <div class="timeline-item">
        <div class="timeline-date">Zeitpunkt C</div>
        <div class="timeline-content">
            <h3>Ereignis C</h3>
            
        </div>
    </div>
</div>