“Tides. In Anchorage Alaska we live on a point located between two enormous tidal bays—so big in fact that Captain Cook on his initial survey of the area thought (hopeful thinking) that this entrance would prove to be a “northwest passage”. It is shallow and all boats traversing to the port are aware of the difficulties involved with a tidal basin considered to be the second largest tide flow in the world. Strangely enough when you go through a tunnel to another port not 1/2 hour away the tidal flow is the exact opposite from the high and low tides near anchorage. Tides are dependent on the moon, sun, configuration of the ocean floor and surrounding land masses—in other words they are complicated. Old tidal clocks attempted to simplify these arrangements by reducing the periods of high and low tides to the moon movements. This works in certain locations, but is generally useless for most areas. If you look up tidal calculations you find that NOAA has great tide tables: Tide Predictions - NOAA Tides & Currents. There is lots of software out there that runs on a computer to generate these tables: JTides Home Page - Arachnoid (this guy is super smart and his web site is wonderful!) But I wanted this thing to be solar-rechargeable, low energy, go unattended for years, not rely on tons of memory, and run by a microcontroller. So I found this guys website: http://lukemiller.org/index.php/2015/11/building-a-simple-tide-clock/ He was able to take the calculations for getting tide height and reduce them into algorithms that are microcontroller size comparable.”