Wristwatch microchip with only discrete semiconductors

https://news.ycombinator.com/item?id=8934474

The device runs off of a 12 volt DC adapter, and the clock’s timing is cleverly inferred from the US standard of running electricity at 60 cycles per second.

Of course, one major characteristic of DC is that it has no "cycles per second", so the above makes absolutely no sense. If the clock is fed by a standard (external) DC supply, it doesn't have access to the cycles of the main power so it can't rely on those.

I would have hoped that someone writing for Make would react when writing that, and actually do some journalism and dig up how it really works.