He learns fast when dragon mating season is it takes maybe 2 cycles for him to start tracking it
There’s been times where it slips Zhongli’s mind bc he doesn’t keep track of the days sometimes and suddenly Childe is telling him “shouldn’t you be getting ready for your rut? You should book a week off of work and we can go grocery shopping later to make sure the pantries are stocked….” And Zhongli sits there like “???” Before he realizes what Childe is talking about

To Zhongli it’s just a thing that happens every few months and is such a hassle to him bc it’s a week of him being sexually frustrated with his dick constantly hard (at least it was pre-Childe era). Meanwhile for Childe it literally is like Christmas and his birthday rolled into one and a full week long of crazy dragon sex