Being able to do scheduled recording is a function of the software that you are using with the SDR hardware. I do not think SDR# supports this function. I do not know of anything Mac native that does. The software that I know of that does support scheduled recording would be SpectraVue, HDSDR, SDRDX, and SDR-Radio Console. Possibly HDSDR and SDR-Radio will support your RTL SDR, so you might give them a try (I have heard they do, but never confirmed it for myself).
T!