Just change the greeting to whatever you want. First just select the weather option & the gear icon there and turn voice off. The problem is the car has not fully established internet connection before the greeting is made so it reverts to the default date in the system before any link is made.
If you want a custom voice greeting, just go to settings, select voice and you can type in any greeting you want.
The woman with the nice English accent will say it once the car is in ready state and all the other software functions have loaded. I wanted her to say "G'day have a nice day" but she doesn't understand Aussie slang & said "Gee day have a nice day" so I changed G'day to Hello.