Not a programmer by trade but I mess around with a lot of the Google APIs for fun. I work in a marketing agency (content strategy) and our team supports dozens of clients. One of the biggest bottlenecks is email response time from clients.

I used the API to go through all of the emails we've received from each client and looked for patterns on date/time of send.

Using that data we get much better response rates by sending emails just before the time when the client will likely be working on email (i.e. the email we send is most likely to be at/near the top of their inbox when they sit down to their computer).