Pre-1995 Patents: Why the Expiration Rules Were Different

In 1994, the US changed its patent term rules as part of adopting the GATT (General Agreement on Tariffs and Trade) treaty. The change affected how long patents last and patents filed before the changeover date follow fundamentally different rules than those filed after.

Any patent filed before June 8, 1995 is subject to the old rules. While most of those patents have long since expired, some are still in force if they had long prosecution histories that delayed their grant.

The old rule: 17 years from grant

Before June 8, 1995, US patents lasted 17 years from the date of grant. The filing date was largely irrelevant to calculating expiration.

Under the old system, strategic applicants could prolong examination indefinitely through a practice called "submarine patenting." By repeatedly amending an application in prosecution, they could keep it pending while a technology developed commercially, then emerge with a patent just when the industry was deeply invested in the technology. The patent would grant and the 17-year clock would start fresh.

The most famous example is Jerome Lemelson, whose submarine patents emerged decades after filing and generated over $1.5 billion in licensing revenue. Many of his patents covered bar code and machine vision technologies that had become industry standards by the time the patents granted.

The 1994 change: 20 years from filing

GATT required US patent terms to be measured from the filing date, not the grant date. The American Inventors Protection Act of 1995 implemented this, establishing the 20-year-from-filing rule that applies to all applications filed on or after June 8, 1995.

The 20-year-from-filing rule eliminated the incentive for submarine patenting. No matter how long you kept an application pending, the clock was running from the day you filed.

The transition rule: whichever is longer

For patents that were in force when the law changed (meaning they had filed before June 8, 1995 and were either already granted or still pending), Congress created a transition rule.

These patents get the longer of:

• 17 years from their grant date
• 20 years from their earliest effective filing date

This meant that applicants who had been gaming the old system didn't get penalized retroactively. If their submarine application finally granted in 1996, they still got 17 years from grant rather than being cut off by the new 20-year filing date rule.

Are any pre-1995 patents still alive?

As of 2026, a patent filed before June 8, 1995 would need to have been granted no earlier than 2009 under the 17-year rule to still be active. Given that most applications take 2-5 years to prosecute, this would require a filing no earlier than around 1990 to create a patent still alive in 2026.

In practice, there are a small number of continuation applications claiming priority to pre-1995 filings that have managed to stay pending and only recently granted, or older patents with PTA that extends them slightly. But the vast majority of pre-1995 patents have expired.

How to calculate expiration for a pre-1995 patent

1. Find the grant date
2. Calculate 17 years from grant
3. Find the earliest effective filing date
4. Calculate 20 years from filing
5. Take the later of the two dates

No maintenance fees could revive this calculation, but fee nonpayment could still cause early expiration.

The Patent Sunset calculator handles pre-1995 patents using this greater-of-two-terms calculation, though given that most have already expired, you'll typically see an "expired" status rather than a future date.

Why this history matters today

Understanding the pre-1995 rules is useful for anyone doing historical patent research, tracing the origin of a technology that's now in the public domain, or working with patent portfolios that span the transition period.

If someone tells you a patent "expires 17 years from grant," they're either describing a pre-1995 patent or they're using outdated information for a modern patent.