The above website has some milestones that you may like to include for a baby- child. It ends at age 5. You may also like to brainstorm things that happened to you if you are stuck for ideas on what happens up to age 12-13.
Your timeline should be a reflection of the big milestones that occur across all areas of health- growth, education, social/emotional and personal.
This website has brief information all the way up to adult. Some of it may be tricky to understand, so you’re going to have to use a number of skills to understand what it’s talking about. Remember not to include information if you’re not sure what it means.