Patent Challenge of the Week: When does a patent expire?

Last week, I wrote about whether an infringement lawsuit can properly be filed at 12:01 am on the date that the patent is scheduled to issue. A plaintiff only has standing to sue once a patent is issued, and it is not clear to me that patent has actually issued by that point (even if the patentee holds exclusive rights for the entire day once the patent has issued).*

Expiration Date: At the other end of the spectrum is the patent expiration date. The language for the new twenty year term reads as follows:

35 U.S.C. 154(a)(2) TERM.-Subject to the payment of fees under this title, such grant shall be for a term beginning on the date on which the patent issues and ending 20 years from the date on which the application for the patent was filed in the United States …

The optional seventeen year term language is parallel to the twenty year term, although slightly different: “The term … shall be the greater of the 20-year term as provided in subsection (a), or 17 years from grant.” 35 U.S.C. 154(c)(1).

The Question: Is the standard patent term (a) twenty years from filing, or is it (b) twenty years from filing plus one day?  I.e., if a patent is set to expire on April 2, 2008, can a generic manufacturer begin to make and sell the product on the morning of the 2nd without infringing? I would initially argue that the term should be (a) twenty years from filing — perhaps primarily because 154(c)(1) refers to the “20–year term.” However, I have heard of generic manufacturers who wait the extra day to be safe. (In certain drug cases, this extra day may be worth several hundred thousand dollars). What is the answer?


  • As a comment noted, Fed. R. Civ. P. 6(a) spells out the rules that courts should “apply in computing any time period specified in these rules or in any local rule, court order, or statute.” Rule 6(a)(1) states that “the day of the act, event, or default that begins the period” should be excluded.  In addition, under Rule 6, a time period is extended if it would otherwise end on a Saturday, Sunday, legal holiday.”
  • 37 C.F.R. 1.7 may also be relevant. 
  • * One bit of hard evidence answering last week’s question comes from dicta in a 1952 Helene Curtis patent case. In that case, the SDNY district court noted that the lawsuit had been filed “fifty-nine minutes after the patent had issued at noon of December 4, 1951” — and thus, was proper. See 105 F. Supp. 886. [Link]

21 thoughts on “Patent Challenge of the Week: When does a patent expire?

  1. 21

    errr….the moment you stop paying maintenance fee…this may be the case within 20 years from the date of filing…but hold on ….generic manufacturers please add 24 hours to that 20 years…you would be absolutely safe… (fyi, in jurisdictions other than US day of filing is included in the 20 years!)

  2. 19

    Basic question: is “midnight” the very end of the day or the very start of the day? I.e., this evening, when your clock says 12:00:00, is that the moment it has changed from 3/31/2008 to 4/1/2008? Or does the date change when the clock displays 12:01:00?

    Or perhaps “midnight” straddles the line between dates, such that 23:59:59 is today, 00:00:01 is tomorrow … but 00:00:00 is nothing? Or 00:00:00 is BOTH?

  3. 18

    From the pharma perspective, if a 17-year patent issued on March 21, 1995 then the patent can be practiced by others starting on midnight of March 21, 2012. This is how patent expirations are listed in the Orange Book, and (without having done an exhaustive study) how the dates are reported to the court in the event of litigation. (In other words, the litigants will inform the court of the expiration date in case an injunction or stay of approval is issued.)

    I am quite certain that the 20-year patents are also calculated in that manner; i.e., a 20-year term means 20 years, not 20 years plus one day.

    Also, although I have not seen the issue arise with respect to patent issuance, I would guess that a court would not fret if a suit was filed at 12:01 AM on the day that a patent issues. For an analogous situation, I can tell you that FDA will accept a Para IV challenge on the day that a patent is listed in the Orange Book, even if FDA hasn’t yet received the listing information from the NDA holder but does receive it that same day. (In other words, the Para IV is filed before the patent is technically listed, but so long as the patent is listed the same day, the FDA accepts the Para IV.)

  4. 17

    Patent term isn’t assessed claim by claim. If you make a priority claim to the parent to file a CIP, the term of the CIP will be based on the parent’s effective filing date even if no claim is eligible for the benefit of the priority claim.

  5. 16

    Would enforcement litigation by a patent holder against only one of a number of infringers permit some kind of defense by that infringer on some kind of laches or antitrust issue (basically, that it wouldn’t be fair for the patent holder to sue against only one infringer while allowing others to infringe)? I think not, because I think the patent holder always has the option to sue or not sue, but on the other hand it does seem unfair, which often seems to carry more weight with a court 😉

  6. 15

    Rule 6(a)(1) states that “the day of the act, event, or default that begins the period” should be excluded. In addition, under Rule 6, a time period is extended if it would otherwise end on a Saturday, Sunday, legal holiday.”

    If we exclude the day of the act, event, or default that begins the period and that day was Sunday (via EFS filing), do we extend the time period so the answer is 20 years plus two days?

  7. 14

    Dennis ,

    There is no doubt that the expiry date of a patent as calculated by the Patent office is 20 years + 1 day from filing or 17 years + 1 day from the date of issue. This calucluation is evident from the fact that the extensions claculated by the patent office start from 20 years + 1 day or 17 years + 1 day from issue.
    for eg Patent No. 4,085,225 which issued on April 18, 1978 was to expire on April 18, 1995 as per the records found on the USPTO website. However it was extended by 2 years and later expired on 18-Apr-97. link to

    So although the Term of the patent as per 35 U.S.C. 154(a)(2) should be 20 years from the date of filing, all actual calculations for patent expiry include 20 years + 1 day.
    This could be a potential topic of resarch for Generic drug manufacturers in case they are to lose several hundred thousand dollars in that 1 day after 20 years. But as Al K. Seltzer has mentioned earlier,if there is some federal statute or court rule and hence the US system of counting does not count the first day as the first day, then Generic Drug manufacturers would be safe in waiting the extra day.

  8. 13

    In patent cases filed under 35 USC 271(e)(2), if the court finds infringement, then, according to 271(e)(4)(A): “the court shall order the effective date of any approval of the drug or veterinary biological product involved in the infringement to be a date which is not earlier than the date of the expiration of the patent which has been infringed.” Pursuant to this statute, the FDA grants final approval to ANDAs on the day of patent expiration–not on the day after patent expiration. Congress could have said, in the statute: “the court shall order the effective date of approval to be a date which is later than the patent expiration date.” But Congress did not say that. Apparently, when Congress drafted 271(e)(4), it considered the patent to be expired on its expiration date, not on the day after.

  9. 12

    Dennis, I think one of the commentators makes a good point above. The answer is “neither.” The stadnard patent term is from the date of issue to twenty years after filing.

    The reason this is important is because your question essentially turns on whether you count the date of issue itself. But since the date of issue, within broad bounds, depends on PTO whim and backlog, the variance is pretty insignificant. It might be very significnat from a absolute dollars point of view, but that just shows how arbitrary PTO action can be. If the PTO chooses to issue your patent a couple of days sooner, you get a lot more money on an important patent (and vice versa if they issue it a couple of days late).

  10. 11

    Patent expires at midnight, 20 years from filing. Thus, a patent issued on March 21, 2002 from a post-GATT application filed on April 2, 2000, will expire at midnight on April 2, 2020. This assumes no terminal disclaimers, no other benefits claimed under 35 USC 120 and no patent term adjustment.

  11. 10

    Clarifying my earlier post:

    A suit can be brought after a patent’s expiration for past damages; however, damages will be limited to at most infringement that occured within six years of filing suit. So if you wait four years after expiration, you’ll only get damages for two years (assuming you survive the inevitable laches defense).

  12. 9

    Bellie: you are correct that a suit can be brought after (up to six years) a patent’s expiration for past damages.

    Ron Laurie and Babel Boy: I’m fairly certain that the expiration of all claims in a single patent rise and fall together, regardless of differences in priority between the claims (e.g., 35 USC 154 defines term with respect to a single patent grant, not multiple grants to individual claims).

  13. 8

    Ron’s got a point.

    The new rules (Where ARE the new rules, anyway?) required that the new matter be designated in a CIP, but that was to facilitate examination. I don’t think it affected patent life.

    My understanding is that 102/103 analysis separates new matter from, old, and the new doesn’t get the benefit of the original filing date. But the whole of the CIP expires 17 years from the priority date. IOW, your new matter is getting shorted.

    This would apply to divisionals with new matter, too, notwithstanding that the CAFC holds that divisionals can’t contain new matter. They haven’t read 35 USC 121:

    “If a divisional application is directed solely to subject matter described and claimed in the original application
    as filed, the Director may dispense with signing and execution by the inventor.”

    Clearly, if a divisional has new matter, a declaration is required, meaning, what else?, a divisional may have new matter.

  14. 7

    …and when does a CIP patent containing claims based on two or more different priority dates expire? Isn’t the expiration date a claim-by-claim analysis?

  15. 6

    From a practical point of view, I wouldn’t think it would matter that much in terms of litigation.
    Even in cases where a single day might be worth a few hundred thousand dollars, I’m not
    sure that would offset the cost of attorneys fees.

    If someone infringes well before the expiration date, I would think you could sue
    for damages caused during that time, even if you didn’t sue for several years later.
    Is this correct? (I’m not an attorney)

  16. 5

    Rule 6. Computing and Extending Time; Time for Motion Papers

    (a) Computing Time.

    The following rules apply in computing any time period specified in these rules or in any local rule, court order, or statute:

    (1) Day of the Event Excluded.

    Exclude the day of the act, event, or default that begins the period.

  17. 4

    Oops. That should be 20 years from filing, of course.

    It was 17 years from issue when I did the research!

  18. 3

    I recall researching this as a young associate, as expiry date can have tax consequences, among other things. My recollection (admittedly 20 years ago) is that the patent expires on midnight on the day after the 20th anniversary. In other words, you dont count the day it issues toward the 20 years.

    Dont rely on this as legal advice, but I think thats the answer.

  19. 2

    The answer is 20 years plus one day. The US system of counting does not count the first day as the first day (there is some federal statute or court rule that tells me so). I don’t feel like looking it up right now — it’s after midnight PDT and I wouldn’t be up except for my acid reflux. Besides we both should be spending our weekend watching hoops instead of counting to 20.

  20. 1

    I am one of the millions of patent prosecutors who sit at the computer each night with bated breath staring at the ole’ inbox waiting for the next PatObv post to arrive. And when it does I un-bate my breath and wallow in the wisdom.

    But dad-burn it all, I think I missed one. Musta’ dozed off. Did you pontificate, or expatriate, or hypothecate, or whatever on the 12:01 AM issue issue?

    I can’t find that sucker. What was the date?

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