Have you kept track of how capitals have changed and will change over time? Only one way to find out! Examples of former capitals would include: Capitals of a dissolved country/entity, a capital moving, military occupation changing a government's location temporarily, etc.
Includes a section of 21st century former capitals
Former nations have the National Flags included for fun! (If it's blank, it's just the modern day flag/no flag)
If a capital is in the same country with the same name today, it isn't counted. This may account for time gaps you see.