Fix time values returned by Cell.dateValue

[MaxDesiatov]

Resolve #114

[codecov]

Codecov Report

Merging #115 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #115   +/-   ##
=======================================
  Coverage   97.34%   97.34%           
=======================================
  Files           8        8           
  Lines         301      301           
=======================================
  Hits          293      293           
  Misses          8        8           

Impacted Files	Coverage Δ
Sources/CoreXLSX/Worksheet/CellQueries.swift	90.32% <100.00%> (ø)

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