This game uses the first year the current national flag design came into use, not just the year it was later formalized in law.

• You are placing countries on a timeline by the first use of their current flag design.
• That year can be earlier than independence, sovereignty, or official standardization.
• Wikipedia separates formal adoption from first use; this game uses the first-use column on purpose.

Some “old” flags are old because the design survived regime changes, redesigns, and standardization tweaks without losing its core identity.