A method comprising: receiving one or more frames sampled from a first media item of an event that is concurrently being streamed to one or more users of a content delivery platform; causing an annotation content analysis of the first media item as the first media item is concurrently being streamed to the one or more users, the analysis to identify annotation content that is relevant to the first media item at a particular timestamp associated with the first media item; analyzing, by a processing device, the one or more frames to identify one or more candidate event clocks within the one or more frames; for each of the one or more frames, determining whether a candidate event clock of the one or more candidate event clocks satisfies one or more conditions; and responsive to determining that the candidate event clock of the one or more candidate event clocks satisfies the one or more conditions, identifying the candidate event clock as an actual event clock used to time the event, and generating mapping data that maps the actual event clock to a timestamp associated with a respective frame of the one or more frames of the first media item, annotating the first media item with the annotation content based on the mapping data, providing the first media item with the annotation content for presentation with an instance of the first media item at a first client device (103A-Z), generating additional mapping data that maps the actual event clock to a timestamp associated with a respective frame of one or more frames of a second media item of the event, annotating the second media item with the annotation content based on the actual event clock and the additional mapping data, and providing the second media item with the annotation content for presentation at a second client device (103A-Z). receiving one or more frames sampled from a first media item of an event that is concurrently being streamed to one or more users of a content delivery platform; causing an annotation content analysis of the first media item as the first media item is concurrently being streamed to the one or more users, the analysis to identify annotation content that is relevant to the first media item at a particular timestamp associated with the first media item; analyzing, by a processing device, the one or more frames to identify one or more candidate event clocks within the one or more frames; for each of the one or more frames, determining whether a candidate event clock of the one or more candidate event clocks satisfies one or more conditions; and responsive to determining that the candidate event clock of the one or more candidate event clocks satisfies the one or more conditions, identifying the candidate event clock as an actual event clock used to time the event, and generating mapping data that maps the actual event clock to a timestamp associated with a respective frame of the one or more frames of the first media item, determining whether a candidate event clock of the one or more candidate event clocks satisfies one or more conditions; and responsive to determining that the candidate event clock of the one or more candidate event clocks satisfies the one or more conditions, identifying the candidate event clock as an actual event clock used to time the event, and generating mapping data that maps the actual event clock to a timestamp associated with a respective frame of the one or more frames of the first media item, annotating the first media item with the annotation content based on the mapping data, providing the first media item with the annotation content for presentation with an instance of the first media item at a first client device (103A-Z), generating additional mapping data that maps the actual event clock to a timestamp associated with a respective frame of one or more frames of a second media item of the event, annotating the second media item with the annotation content based on the actual event clock and the additional mapping data, and providing the second media item with the annotation content for presentation at a second client device (103A-Z).