The time service is only intended for testing and is only available in static time mode. You can turn on static time via daml sandbox --static-time. Take a look at Is it possible to start Canton Sandbox in static time mode, specified in the `daml.yaml` file? - #2 by cocreature for some caveats if you try to do this in daml start.
As for detecting whether you’re in static time mode, you can catch the unimplemented exception. Navigator does something like this here daml/PlatformStore.scala at f4211b709ffd31453ed94b99538c6434647f520d · digital-asset/daml · GitHub.