Hello,
Based on my experience, I feel confortable to resolve the bug you're facing with the Date Timezones.
This is hard to say at this moment how much effort this would take as it varies on the existing code + the librairies available in your React project to handle date format, but I can guarantee you to stick in the budget you propose.
You can expect from me full transparency and quality in my delivery.
Best regards,
Julien Vanden Dries