If you want to keep php out of your template, but still be able to use php string manipulation you could use CE String to do so.
This will allow you to use datetime conversion without directly writing out php code as well as any other php that you might need. Its pretty powerful.
I'm sure that there are other extensions and plugins that could handle datetime as well - perhaps Low Nice Date?
Otherwise, it would be easy enough to do in jquery on page load as well.
edit: after looking at a few other plugins, I think Low Nice Date is the way to go. Its simple, free, and works for EE2 and EE3.