Here is a timeline with timestamps on the left and entries on the right, as you scroll through the timeline the timestamp gets fixed to the screen as the entries on the right scrolls through. This is great when you have lots of entries in each timeslot.

If you are having trouble with the pen, try the archived copy on GitHub

Fixed Header Timeline Snippet

See the Pen Bitcoin timeline with fixed header using flexbox by Matys (@mathiesjanssen) on CodePen.0