Actually we may remove time zones all together too. So the day time of 3pm will be different everywhere. For calendar months and seasons we already have it like that, in both hemispheres. The only issue is backward incompatibility with legacy movies, books who talk about breakfast at 8am. Similarly, a love song which talks about April/May being a sunny warm time sounds weird in southern hemipshere. Let's get rid of Roman legacy code in our civilization :)