Sharepoint custom webpart don't sort proberbly in production

Question

We have created a picture-sharing web part. that gets data from 3 different SharePoint lists.

When I want to show the latest 3 posts in my production environment, it gets sorted differently.

The custom web part is written in typescript/react

I have tried.ToISOString .ToString and modified it to numbers

but these work in my local environment. but when I do gulp package-solution --production

and upload it to our SharePoint. It won't sort from the latest to the oldest correctly.