When is client-side modified being added?

Hello Openstack When is client-side modified being added as a new feature? Right now I'm paying for file hosting and when I upload a file, the "date modified" isn't respected for that file. It always takes the "date modified" for the file as the current date, not the one on the file I was uploading from my computer. I've contacted the company I brought it from, and they said that client-side modified isn't supported in the Openstack API <https://docs.openstack.org/swift/latest/s3_compat.html>. What API method would this be exactly? Would it be the "object tagging" method? Do you lot have any idea when this feature would be added in, so my file uploads will respect the "date modified" metadata?