Событие timeupdate
<video id="video1" controls autoplay loop src="https://sample-videos.com/video123/mp4/240/big_buck_bunny_240p_1mb.mp4"></video>
<output id="out"></output>
<script>
video1.addEventListener("timeupdate", (last => ({ target }) => {
var p = target.currentTime >= 2; // или другое время вместо 2-ой секунды
if(p && p !== last) {
out.append(document.createElement("br"), "Event!", target.currentTime);
}
last = p;
})());
</script>
Или playing, если нужно вначале
<video id="video1" controls autoplay loop src="https://sample-videos.com/video123/mp4/240/big_buck_bunny_240p_1mb.mp4"></video>
<output id="out"></output>
<script>
video1.addEventListener("playing", ({ target }) => {
if(target.currentTime < 1) out.append(document.createElement("br"), "Event!", target.currentTime);
});
</script>