The Hackaday Prize rules ask for answers to a few specific questions:

1. What are the challenges the project addresses?
2. How does the instant project address those challenges?
3. How does solving those challenges change the world?

The Global Positioning System was fundamentally designed to solve the problem of navigation - knowing where you were in space (relative to the Earth). But solving that problem fundamentally required distributing hyper-accurate time. And providing accurate timekeeping is a secondary goal of GPS. GPS has been widely used in industry and science as a source of accurate time (and from it accurate frequency references, etc).

For consumers, so-called "Atomic" clocks are available at premium prices in relatively pedestrian retail stores. Such clocks are actually radio clocks (as are GPS clocks), but their source is the WWVB 60 kHz time signal broadcast from Ft. Collins, CO. This signal is only really available in North America, its availability varies widely, and the accuracy of such clocks depends on that level of availability. The attraction of those clocks largely is that they set themselves and automatically corect for Daylight Savings Time. They typically run on batteries which usually need to be replaced at least annually.

GPS reception is much more available not only around the world, but in North America it relies merely on line of sight reception from the GPS satellites, which are in orbits that move around. Because of that, continuous GPS coverage is easier to obtain than WWVB (where continuous availability is limited to only a few states surrounding Colorado). Because of this a GPS clock doesn't have to maintain its own accurate timekeeping - it can count on continuous service from the GPS system to tell it the current time.

WWVB's timecode includes DST status, but only for the US (which is sensible given the fact that its coverage area is limited). GPS does not, but GPS includes the date, which is sufficient for a clock to compute DST on its own. In fact, the GPS clock includes rulesets for the EU, Australia and New Zealand in addition to the US (and you can also turn DST off). Adding additional DST rulesets would simply require adding them to the firmware (the same goes for ruleset changes).

The idea of a clock that sets itself and displays accurate time without any need for maintenance has been made possible by GPS, but that same facility has not been made available routinely to consumers other than via radio clocks limited to use within a particular region. Every modern smart phone or Internet connected computer can obtain accurate time over the Internet, but using something like that as a simple standalone clock would be swatting a fly with a sledgehammer.

Everything about the design of this project has been about balancing accuracy against cost. No other product of which I am aware offers a display granularity of 100 ms, an accuracy of under 200 µs, and a price tag under US$150.