Is there any way to change the git push date or devops push date timestamp in the repository?

No, it is not possible to change the push logs in Azure DevOps.

Note that in general, you can't fully trust Git commit dates and authors. In AzureDevOps, you can trust the Push Logs, as well as the history of Pull Requests. If you could modify the Push Logs you wouldn't be able to trust those either.