Use datetime.now instead of datetime.utcnow.

[dajiaji]

No description provided.

[codecov]

Codecov Report

Merging #179 (84a50f8) into main (6a3eb96) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #179   +/-   ##
=======================================
  Coverage   99.84%   99.84%           
=======================================
  Files          28       28           
  Lines        2604     2604           
  Branches      676      676           
=======================================
  Hits         2600     2600           
  Misses          4        4           

Impacted Files	Coverage Δ
cwt/cwt.py	100.00% <100.00%> (ø)

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