Update 03-dates-as-data.md to update link to Microsoft's explanation of Excel dates

[kylamj]

updating the link for Microsoft's explanation of Excel's date systems

If this pull request addresses an open issue on the repository, please add 'Closes #NN' below, where NN is the issue number.
$170

Please briefly summarise the changes made in the pull request, and the reason(s) for making these changes.
Issue reported states that link explaining the 1900 date system is broken. I located the correct link, morskyjezek agrees it is the correct link. This pull request updates the link in the lesson to the new link.

If any relevant discussions have taken place elsewhere, please provide links to these.

For more guidance on how to contribute changes to a Carpentries project, please review the Contributing Guide and Code of Conduct.

Please keep in mind that lesson Maintainers are volunteers and it may be some time before they can respond to your contribution. Although not all contributions can be incorporated into the lesson materials, we appreciate your time and effort to improve the curriculum. If you have any questions about the lesson maintenance process or would like to volunteer your time as a contribution reviewer, please contact The Carpentries Team at team@carpentries.org.

[github-actions]

Thank you!

Thank you for your pull request 😃

🤖 This automated message can help you check the rendered files in your submission for clarity. If you have any questions, please feel free to open an issue in {sandpaper}.

If you have files that automatically render output (e.g. R Markdown), then you should check for the following:

• 🎯 correct output
• 🖼️ correct figures
• ❓ new warnings
• ‼️ new errors

Rendered Changes

🔍 Inspect the changes: https://github.com/LibraryCarpentry/lc-spreadsheets/compare/md-outputs..md-outputs-PR-171

The following changes were observed in the rendered markdown documents:

 03-dates-as-data.md | 2 +-
 md5sum.txt          | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

What does this mean?

If you have source files that require output and figures to be generated (e.g. R Markdown), then it is important to make sure the generated figures and output are reproducible.

This output provides a way for you to inspect the output in a diff-friendly manner so that it's easy to see the changes that occur due to new software versions or randomisation.

⏱️ Updated at 2025-09-16 13:30:27 +0000