Hope someone is reading this as is an old original post.
Surprised you got no anwers. I have a similar problem in that I want to implement a ready by routine. Some call it prewarm but my seach for “prewarm” here only came up with one not very relevant post and “ready by” is barely mentioned either.
A colleague did it before on a Pi and it’s not easy as the software has to coninuously look ahead several hours to see what ON events are coming up. Then work out when to start the boiler based on current temperature and the thermal mass of the building. He used a fixed thermal mass, like 4C rise per hour, based on experiment.
But Hive is more clever in that it works out this thermal mass based on past history. And if it does it correctly it should reassess the result every month or two ( or continuously) as it varies with the outside tempertures, as losses are higher and wall tempertures are lower in the winter.
I need a 5 hour look ahead but Hive only does 1 hour, maybe because the processor load of all this is high and 5 hours makes it higher.