After a long pause we have more updates to the flespi analytics engine.
First of all it is possible to use date/time functions in expressions - month(X), day(X), hour(X), minute(X). This can be used for intervals validation e.g. hour(begin)>8 or just to filter some messages with hour(X)>12 if you need to detect intervals for some shifts only. Any kind of usage of course.
And additionally we have added active MQTT topic for device assigned to calculator. It will contain the same value as last whenever last detected interval is active at the moment. Once it is no more active null will be published into MQTT. active topic can be used as a foundation for analytics-based own notifications system.