Your response doesn’t quite characterize the rate limits themselves, though.
One does not hit a rate limit and then have to wait until 00:00 UTC to be able to make another call.
Nor is it as straightforward as ChatGPT Plus, where you must wait for that 1st message to expire from the three hour window before you can send number 41.
After a reset as I describe in my earlier reply, the API is memoryless of what you did. 5 calls now, and 100 more available in a few hours.
It can be described as “you can operate continuously at a maximum rate that approaches your daily rate limit”, a description equally confusing.
Billing is indeed based on UTC time, where one could see the next day roll over when expanding by hour and then minute, adjusted to the local time. Now it is completely opaque, the answer about billing only informing us which bin in the bar chart calls are placed in.