"The Cricket!" by Street Electronics Corporation, released in 1984, is a hardware peripheral for the Apple //c computer. It plugs into the serial port and offers a multi-voice sound synthesizer, a speech synthesizer, and a real-time clock.
I ended up disassembling both [NS.CLOCK.SYSTEM](ns.clock.system.s) (to understand the SYSTEM chaining - what a pain!) and The Cricket!'s [PRODOS.MOD](prodos.mod.s) and melding them together, adding in the detection routine following the protocol in the manual.
* [SET.DATE](set.date.s) sets the Cricket's current date.
* [SET.TIME](set.time.s) sets the Cricket's current time.
Also, an updated [NS.CLOCK.SYSTEM](ns.clock.system.s) is included that fixes a typo, removes beeps, and is less chatty so you can have both `NS.CLOCK.SYSTEM` and `CRICKET.SYSTEM` in the same hard disk image if you use the image across different hardware configurations.