Interesting use case - im not 100% sure if you can set it for that, You can however set a maintenance window to ignore alerts in the time frame where there is no traffic.
The other thing is to allow DAVIS UI to baseline the data, so if there is no traffic from 6-6, then that will become a norm, and after a week or so, you wont get alerts of low traffic.
Very interesting use case, maybe others will have a solution other then a reoccurring daily maintenance window and letting DAVIS Baseline the data
custom alerts can only be used to examine an hour interval max. Davis will learn the pattern for still as an hourly pattern, hence if your system one night has 5 requests at 11 and then 2 and 4 and then on the other night it’s on different hours, DAVIS will probably won’t be the answer for that.
As you’re looking at a 12 hour interval and I assume these are the same hours, I would go for a simple API call from a shell being run at (let’s say) 05:59, summing up the number of requests for the past 12 hours and if needed creates an alert.
You would need the metrics API and the events one. Should be relatively simple.