pdfdate

Retrieves the creation/modification date of a PDF document.

The problem

You enjoy reading technical reports and downloaded a bunch of PDF files, but their time stamps are all wrong - it's the time of the download, not the CreationDate/ModificationDate of the document, which is likely to be in the past. But having proper timestamps is useful to know when a report was actually written. What can you do?

$ll
total 8.2M
-rw-r--r-- 1 holger users 632K Jul 30 13:18 A Glimpse of the Matrix - Scalability Issues of a New Message-Oriented Data Synchronization Middleware.pdf
-rw-r--r-- 1 holger users 458K Jul 30 13:18 Analyzing the Performance of WebAssembly vs. Native Code.pdf
-rw-r--r-- 1 holger users 2.2M Jul 30 13:18 Avoiding Scalability Collapse by Restricting Concurrency.pdf
-rw-r--r-- 1 holger users 365K Jul 30 13:18 Bipartisan Paxos - A Modular State Machine Replication Protocol.pdf
-rw-r--r-- 1 holger users 646K Jul 30 13:18 Exploiting Commutativity For Practical Fast Replication - Slides.pdf
-rw-r--r-- 1 holger users 811K Jul 30 13:18 Exploiting Commutativity For Practical Fast Replication.pdf
-rw-r--r-- 1 holger users 1.3M Jul 30 13:18 Exploiting a Natural Network Effect for Scalable, Fine-grained Clock Synchronization.pdf

A nonsolution

You open every document, manually inspect its properties and use touch to fix every timestamp individually.

Just kidding, of course you don't.

The solution

$for f (*.pdf) d=$(pdfdate $f) && touch -d "$d" "$f"
$ll 
total 8.2M
-rw-r--r-- 1 holger users 632K Dec 2 2019 A Glimpse of the Matrix - Scalability Issues of a New Message-Oriented Data Synchronization Middleware.pdf
-rw-r--r-- 1 holger users 458K Jan 29 2019 Analyzing the Performance of WebAssembly vs. Native Code.pdf
-rw-r--r-- 1 holger users 2.2M Jul 15 2019 Avoiding Scalability Collapse by Restricting Concurrency.pdf
-rw-r--r-- 1 holger users 365K Mar 3 01:49 Bipartisan Paxos - A Modular State Machine Replication Protocol.pdf
-rw-r--r-- 1 holger users 646K Feb 28 2019 Exploiting Commutativity For Practical Fast Replication - Slides.pdf
-rw-r--r-- 1 holger users 811K Feb 23 2019 Exploiting Commutativity For Practical Fast Replication.pdf
-rw-r--r-- 1 holger users 1.3M Apr 30 2019 Exploiting a Natural Network Effect for Scalable, Fine-grained Clock Synchronization.pdf

This will fix up all timestamps. Invalid documents or missing CreationDate/ModificationDate properties are ignored. If a document contains both properties then the latest value is preferred.

Building

• Install poppler and - depending on your distribution - poppler-dev
• c++ -pipe -Os -Wall pdfdate.cpp -o pdfdate -lpoppler-cpp
• install pdfdate to /usr/local/bin or some other part of your $PATH.

Enjoy! :)