What's the date of the little sky in big warehouse that the old man said?

How many days have it been? Summer is dog days. "Three volts" refers to the first, middle and last three volts, which is about mid-July to mid-August. After the summer solstice, although the days are getting shorter and the nights are getting longer, the days are longer than the nights in a day. Every day, the ground absorbs more heat than it emits, and the temperature near the ground is getting higher every day.