Key Takeaways

  • The list of patents by date can be compiled using several databases, including USPTO, Google Patents, Espacenet, and LexisNexis Academic.
  • Patent priority and issue dates are critical when tracking innovation timelines or establishing rights during litigation.
  • Searching by classification, inventor, or assignee provides a deeper look into related patents, technologies, and ownership changes.
  • The priority date determines which application has the earliest claim to an invention — vital for patent disputes and prior art analysis.
  • Tools like Google Patents Advanced Search allow users to refine searches by date range, patent type, and jurisdiction.
  • Understanding how to verify patent ownership and litigation history can prevent infringement and strengthen due diligence

To find a list of patents by date, there are a number of searches you can use.

A patent number is the best option to search for patents. Since patent numbers can be found on produced goods, collectors can use this to access information on an antique object.

If you have the U.S. patent number, a full-text patent can be pulled up in Google Patent Search, the U.S. Patent & Trademark Office website, or the pat2pdf website. Most free patent search sites let you to use this information to obtain a PDF version. 

If the patent number isn't available, but the patent was issued after 1975, you can search using inventory or topic using Espacenet or Google Patent website. Patents issued between 1790 and 1975 can only be found through the USPTO search and require the patent number, U.S. classification, and issue date.

The Google Patent Advanced Search permits users to search by inventor, patent number, assignee, classification number, topic, and date. This applies to patents issued before 1975. These results can be refined using the “Search Tools,” which limits the search by publication date, issue date, filing status, patent type, and patent office.

To find a patent when you only know the assignee or patentee, you can search Espacenet or Google Patent by keywords. The Advanced Search in Google Patent allows you to search by fields.

If you don't have a particular patent to find, you can search by subject using Google Patent or Espacenet website by keyword or search the USPTO database using the 7-Step U.S. Patent Search Strategy. You can also search for a particular discipline and refine the search to only show patents.

Patents issued from 1976 to present are full-text searchable by keyword. This can be entered into the Quick Search or Advanced Search query box. You can also limit the keyword search to a specific field using both the Quick Search and Advanced Search.

Some fields that help you search for patents include:

  • Inventor name
  • Patent number
  • Description 
  • Specifications
  • Claims

Using the LexisNexis Academic Database

The LexisNexis Academic, a campus-wide research database, can be accessed through the Hesburgh Library and provides a variety of news, legal, business, and reference information. This covers patents from 1790 to present. Patent information prior to 1971 are in semi-full-text format and can only be searched by certain fields. Patents after 1971 are fully searchable and are in full-text. This information is available under the U.S. Legal heading.

To use LexisNexis Academic, you must create a keyword search that uses the purpose, use, and composition of an invention to find its proper classification. Then, you can use the keyword search to find patents and collect helpful classes and subclasses, which allow you to find more patents in LexisNexis Academic.

Searching by patent number, assignee, or inventory name is easy with LexisNexis Academic, since there are specified search boxes for each type of search.

To obtain a list of expired patents, you can use the U.S. Patent Full-Text Database Manual Search. You can search by the patent filing date or by the range since a patent lasts 20 years from the original date of filing.

Understanding Patent Priority Dates and Their Importance

A crucial concept when reviewing a list of patents by date is the priority date. The priority date represents the earliest filing date that a patent application can claim. This date establishes the inventor’s right to the invention against later filings by others. For example, if two inventors file similar applications, the one with the earlier priority date will generally have superior rights.

The priority date can be derived from:

  • The original patent application filing date.
  • A provisional application filed earlier for the same invention.
  • An international filing under the Patent Cooperation Treaty (PCT).

When sorting patents by date, distinguishing between filing, publication, issue, and priority dates ensures accuracy in assessing innovation timelines. Many patent searches, including those in USPTO or Espacenet, allow filtering results by these date types, making it easier to identify the first instance of invention disclosure.

Searching by Patent Classification

Here are the steps to searching by patent classification:

  1. Think of keywords that describe the purpose, use, and composition of an invention.
  2. Then search the index to the U.S. Patent Classification and choose “Index in HTML” format. This supports the linking to the next step.
  3. The index allows you to use common terms to find the classes and subclasses for an invention with an alphabetized list of subject headings.
  4. The next step is examining the Classification Schedule in the Manual of Classification, which can be found by clicking the blue 297 hyperlink.
  5. The Classification Schedule shows the several classes and subclasses within the system.
  6. This allows you to prove that the classes and subclasses in the index are relevant, which improves your search results.
  7. To move to the Classification Definitions, click the blue 195.13 hyperlink. This is useful if you're having trouble deciding between classes or subclasses, since there are definitions regarding the subject matter in each class. This also shows the distinctions between classes and subclasses and refers you to those that are related.
  8. A list of all patents issued and all applications are then found by clicking on the red icon to the left of the subclass number in the Manual of Classification for patents issued. The blue icon to the left of the icon is for pending applications. 

How to Find Patents by Law Firm, Assignee, or Inventor

Beyond searching patents by classification, users can refine a list of patents by date by looking up patents associated with specific inventors, assignees (companies that own the patents), or even law firms that filed the patents.

Platforms like Google Patents, Espacenet, and the USPTO Assignment Database make this process accessible:

  • By Inventor: Enter the inventor’s name in the advanced search bar and sort results chronologically.
  • By Assignee: Search by the business or institution that owns the patents.
  • By Law Firm or Attorney: Some databases like the USPTO PAIR or legal research tools such as LexisNexis display the attorney or firm that filed the application.

This type of search can be especially helpful for due diligence or competitive intelligence. For example, a company assessing its competitors’ R&D strategies might use these searches to track new filings or expired patents.

Using Patent Dates in Litigation and Prior Art Research

Patent dates play a significant role in intellectual property litigation. The filing date and issue date establish when rights begin and end, while the priority date determines which invention came first in a dispute. Courts often analyze these dates to resolve conflicts over novelty, infringement, and validity.

When building a patent litigation case or conducting a prior art search, legal teams frequently compile a list of patents by date to:

  • Identify earlier inventions that may invalidate a newer patent.
  • Trace ownership and licensing transfers.
  • Determine whether a patent has expired (typically 20 years from the earliest filing date).

Organizing patents chronologically provides a clear snapshot of an industry’s innovation timeline, helping attorneys and inventors evaluate potential infringement risks or commercialization opportunities.

Tips for Organizing Patent Data Effectively

Once you’ve gathered a list of patents by date, organizing the information is key to drawing useful insights. Best practices include:

  1. Sort by Key Date Types: Separate columns for priority, filing, publication, and issue dates.
  2. Include Patent Identifiers: Record patent numbers, inventors, and assignees.
  3. Track Status: Note whether each patent is active, expired, or pending.
  4. Link Classifications: Add the U.S. or international classification for subject-matter grouping.
  5. Use Digital Tools: Export data from USPTO, Espacenet, or Google Patents into spreadsheets for easier analysis.

Properly structured lists allow businesses, researchers, and law firms to quickly identify patent trends, expiration timelines, and innovation milestones.

Frequently Asked Questions

  1. What is the difference between a filing date and a priority date?
    The filing date is when the application is submitted to the patent office, while the priority date is the earliest claim to the invention, often from a provisional or earlier filing.
  2. How can I search for patents issued on a specific date?
    Use USPTO or Google Patents Advanced Search, entering a date range under “Issue Date” or “Publication Date.”
  3. Can I find patents filed by a specific law firm?
    Yes. USPTO PAIR and private databases often list the attorney or law firm of record, which can be searched by name.
  4. What’s the easiest way to compile a chronological list of patents?
    Search by keyword or inventor, then use the sort function in patent databases to arrange by date. Export results to Excel for analysis.
  5. Why are patent dates important in litigation?
    They establish who filed first and help determine patent validity, priority, and expiration in infringement or invalidation cases.

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