Hacker News Reader

In 1995, it was changed from 17 years counting from the issuance of the patent to 20 years counting from the earliest filing date. It is not clear whether this should count as an extension or not--it is 3 more years, but the clock starts running earlier.

Before that, the only extension of the patent term was from 14 years to 21 years, which happened in 1836. In 1861, it was shortened to 17 years.

Yes. The clock starting at filing change was due to submarine patents (people would keep things in process for many years, and slowly amend them, until when they finally issued, they covered whatever was cool at the time. There are a few famous examples).

Realistically, the life of the average patent was not extended by this change, since patent apps, on average, were taking three years to approve.

Something both parties will agree on...

I think US is trying to extend patent life to 30 years or something in the TPP.