fix date time access

[BeastyBlacksmith]

Description

Used Dates.value instead of the current solution.

Fixes #5034 for Plots v1

Attribution

• I am listed in .zenodo.json (see How to get acknowledged #3503)

Things to consider

• Does it work on log scales?
• Does it work in layouts?
• Does it work in recipes?
• Does it work with multiple series in one call?
• PR includes or updates tests?
• PR includes or updates documentation?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.02%. Comparing base (fa65e7d) to head (76cc9ae).
Report is 34 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5052      +/-   ##
==========================================
- Coverage   89.77%   89.02%   -0.75%     
==========================================
  Files          40       40              
  Lines        8780     8246     -534     
==========================================
- Hits         7882     7341     -541     
- Misses        898      905       +7     

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