Daily Email Limits, by calendar day or 24h clock?

[Geoff_Krajeski1]

My team would like to know if the daily email limit is based on 24hr clock, or calendar day.  

It does not specify anywhere on the community that I could find or in this article: https://community.marketo.com/MarketoArticle?id=kA050000000LAoDCAW

[Kenny_Elkington]

Adam is correct that it is calendar day, except that the window is based on instance time, and not on data-center time.

[Anonymous]

WARNING: I am not an employee. I don't have the correct answer. But if I were to guess, I'd say it's a calendar day as defined where Marketo's initial data center resides. My assumption is 12-12 PST. 

I don't know for certain, but I doubt that they are simultaneously calculating for billions of leads whether over 24 hrs have X number of emails had been sent. It just seems more memory efficient to do calendar day/week.