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Understanding different types of timestamps

The create and modify timestamps can be somewhat confusing, so here is a brief explanation of what they are and how they are used.

There are two different sets of timestamps when it comes to PDF files:

  1. Operating system timestamps
  2. PDF Metadata timestamps

Operating system timestamps

These are the timestamps that your operating system uses to track when a file was created and last modified. They are not part of the PDF file itself, but rather part of the file system where the PDF is stored.

The operating system timestamps are typically used by the file manager to display when a file was created and last modified.

These timestamps are usually set when the file is created and/or updated by the operating system, for example when you download a PDF file it will have Created/Modified timestamps set to the time of download.

Here is where you can find these timestamps in Windows:

File Explorer timestampsFinder timestampsFiles timestamps

You can modify these timestamps in the File Properties Tab in the Desktop App:

File Properties Tab

PDF Metadata timestamps

There are actuially stored in the PDF file itself and are part of the PDF metadata. These timestamps are usually displayed in the Document Properties dialog in PDF viewers.

Pdf Document Properties

And in Pdf Metadata Editor you have the following options to change them:

Document timestampsXmp timestamps

As you can notice there are two separate fields for each value. This is due to how the PDF standard has evolved. The Document properties ( or the Info dictionary ) is the older standard to specify metadata, and the XMP is the newer hence the duplication.

Generally when they are displayed by a reader, the XMP settings take preference. The Document values are shown only if the relevant XMP fields are empty.