Clarification needed: Public domain file in Apache 2.0 licensed project - tzfile.h

[rmnblm]

Hi there 👋

I hope this finds you well. I’m reaching out regarding a licensing question that requires clarification for compliance purposes.

Background:
While conducting a FOSS license analysis of our company's project dependencies, I discovered that the file absl/time/internal/cctz/src/tzfile.h in your repository contains a public domain declaration:

/* ** This file is in the public domain, so clarified as of ** 1996-06-05 by Arthur David Olson. */ 

Questions:

• Why does this specific file have a different licensing status (public domain) compared to the rest of the Apache 2.0 licensed project?
• Would it be okay to use this file under Creative Commons CC0 v1.0 Universal License (CC0 v1.0)? The Swiss law do not recognize a permanent relinquishment of Copyrights as the Public Domain provides for.
• Could you provide a written statement confirming the licensing status of this file and whether it can be used independently of the Apache 2.0 license that covers the rest of the project?

Context:
I need this clarification for our company's legal compliance documentation, as mixed licensing within a single project can create uncertainty about usage rights. A clear written statement from the project maintainers would be extremely helpful for proper attribution and compliance.

Thank you for your time and for maintaining such a valuable library for the C++ community. I look forward to your clarification on this matter.

Best regards,
Roman