Fix single digit date parsing

[RenjiSann]

Fixes uutils/coreutils#6392

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 71.21%. Comparing base (1389991) to head (1bb93d7).

Files	Patch %	Lines
src/lib.rs	66.66%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #76      +/-   ##
==========================================
+ Coverage   70.24%   71.21%   +0.97%     
==========================================
  Files           6        6              
  Lines         820      820              
  Branches      195      190       -5     
==========================================
+ Hits          576      584       +8     
+ Misses        135      127       -8     
  Partials      109      109              

Flag	Coverage Δ
macos_latest	70.00% <66.66%> (+0.85%)	⬆️
ubuntu_latest	69.02% <66.66%> (+0.85%)	⬆️
windows_latest	7.62% <0.00%> (ø)

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[cakebaker]

Thanks for your PR :)