[stable5.0] fix: send date as string instead of epoch

[backportbot]

Backport of PR #6532

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 15.43%. Comparing base (459f41a) to head (dad9740).
Report is 9 commits behind head on stable5.0.

Files with missing lines	Patch %	Lines
src/services/appointmentService.js	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           stable5.0    #6565   +/-   ##
==========================================
  Coverage      15.43%   15.43%           
==========================================
  Files            206      206           
  Lines           9441     9441           
  Branches        2204     2204           
==========================================
  Hits            1457     1457           
+ Misses          7666     7665    -1     
- Partials         318      319    +1     

Flag	Coverage Δ
javascript	15.43% <0.00%> (ø)

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