Conversation so far:
how did japan's postwar constitution compare to the us constitution
The new constitution did not attempt to impose a United States-style presidential or federal system. Instead, the proposed constitution conformed to the British model of parliamentary government.
when was the new japanese constitution enacted
The Japanese Constitution was enacted on 3 May 1947, as a new constitution for a post-war Japan.
what is special about The Japanese constitution
The Japanese constitution is the oldest unamended constitution in the world.

Question: how long has the constiution been unamended
Self-contained rewrite: how long has The Japanese constitution been unamended