If you want a fixed standard time, we already have UTC, - get used to it and the offset of the _local_ times you need to know.
Also, just like you don't need to remember timezones today (you can just google them), you won't need to remember daylight hours (or whatever the terminology will end up being) in a single timezone future (because Google will know)!
Also, once you know the easy-to-remember-or-lookup offsets of the locations you interact with you can even translate in your head to save others the effort.
Yes! Why have a single, standard system known as timezones when each and every calendaring app can have their own "not a timezone" timezone mappings. That way Apple, Google and Microsoft can have three incompatible mappings between UTC and local time.... er.... accepted local customs. It will be great!
Have you ever considered that people might be just assholes? :)
This is a weak argument for keeping timezones around imo.