Use LocalDateTime in birthday tests

[snuyanzin]

No description provided.

[what-the-diff]

PR Summary

• Simplification of import statements
  The file DateAndTimeTest.java had some unnecessary imports for java.util.Calendar and java.util.GregorianCalendar which have now been removed.

• Updating method for calculating date
  The method of calculating 'from' and 'to' variables in the testBirthday() method has been modernized. It now uses LocalDateTime and ZoneId instead of the older Calendar and GregorianCalendar.

• Stabilizing the date variable
  The date variable has been reassigned as final, improving the robustness of the code by preventing unwanted modifications.

• Assert statement improvements
  The assertion check, which helps in verifying the correctness of the code, has been updated. It now uses assertThat method in place of assertEquals, offering a more fluent interface and flexible testing capabilities.

• Refining the 'assert' condition
  In the assertThat condition, we now validate if the birthday timestamp is less than to instead of comparing it for equality. This change allows for a more flexible date and time comparison.

• Updated comments
  To provide clarifications and enhance readability, the comments detailing changes in the code have been updated.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.33%. Comparing base (b37c566) to head (1f2a3ed).
Report is 15 commits behind head on main.

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Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1100      +/-   ##
============================================
- Coverage     92.35%   92.33%   -0.02%     
- Complexity     2821     2822       +1     
============================================
  Files           292      292              
  Lines          5609     5610       +1     
  Branches        599      598       -1     
============================================
  Hits           5180     5180              
  Misses          275      275              
- Partials        154      155       +1     

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