> Why is calendaring hard? Well, [...] the product requirements [...] some sort of ridiculous amount of distributed systems hackery around timeliness of updates

> Why is calendaring hard? Well, [...] the product requirements [...] some sort of ridiculous amount of distributed systems hackery around timeliness of updates, heterogenous network, consistency, graceful exception handling, and node availability semantics. I'm sure Facebook, Google, Apple or Twitter can do that.