Multiple time ranges, buffer times, real-time conflict checks against your calendar, and a public page that respects whoever's reading it.
Most calendars assume a single block per day. Most actual workdays don't work that way. Kaien lets you set 9am–12pm and 2pm–6pm as two separate windows, on every day of the week.
A meeting that ends at 2pm and a meeting that starts at 2pm is two meetings. Add a 5, 10, or 15-minute buffer to any event type. Kaien hides slots that would violate it.
Calm typography, generous whitespace, the visitor's local timezone detected automatically, and slot times shown in tabular numerals so they don't shift as you read down the list.