An empty day in a Timeline project can have different states that are represented by colors and icons depending on the content in your Photos app.
- If a date has a dark seaweed color it means that there's no videos or photos available for that day in your library. However, you can add content recorded on a different date to it.
- If a date is represented in a teal/aqua color it means that there's content for that day in your library.
- A video camera icon means that you have at least one video available for that day.
- A camera icon means there's only photos available for that day.
- Today is represented in a cyan color.