Stop DateTimeDiff message tests from racing the clock

[alganet]

The "Without adjacent result" tests validated "1 year ago" against positive() and between(2, 5), expecting both rules to fail so that AllOf reports "must pass all the rules".

DateTimeDiff reads the clock for $now and only then parses the input, so a relative input reads the clock a second time. When both reads land in the same microsecond the difference is exactly one year and the comparison value is 1 instead of 0, positive() passes, and AllOf reports "must pass the rules" instead. Running the file alone hides it; in the full suite, with caches warm, roughly half the runs failed.

Move the input a minute off the boundary so the number of years is always 0, the same idiom the documentation already uses. The underlying validator remains sensitive to inputs that fall exactly on a boundary.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.12%. Comparing base (56239ca) to head (c5a4c64).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #1833   +/-   ##
=========================================
  Coverage     97.12%   97.12%           
  Complexity     1069     1069           
=========================================
  Files           198      198           
  Lines          2505     2505           
=========================================
  Hits           2433     2433           
  Misses           72       72           

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