I tend to aim for almanac guidelines. But I am more tuned in to your issue of how to handle heavy clay. Drainage is key. I subscribe to the school of growing above the clay, a la "no dig" gardening methods.
Two benefits. Your back will thank you, and you prevent the "soup bowl" effect that traps water and potentially drowns plants' roots. You can make formal raised beds, but more easily you can just layer amendments on top of the soil. Numerous no-dig videos exist on you tube.
Years ago I heard of the ancient farming adage "New moon supports beginnings/plantings, full moon supports endings/harvesting." It makes sense to me that throughout time, humans paid attention to the results of how they timed their gardening and results.
Weather will vary little year to year on average according to the lunar calendar, so most people that pay attention to weather cycles will look at the point you are in the lunar cycle to try and predict whether you are too early to plant or not. Again this is only the average and doesn't predict any single planting season. I also look at the long term weather forecast and whether my back hurts or not.