EquationOfTime

Equation of Time

Measures the variation of the lengths of days throughout a year. For example, during parts of the year, days can fluctuate by around 20 seconds above or below 24 hours. This is caused by the Earth’s orbit around the sun being slightly elliptical and the sun’s eastward passage throughout the year being fastest at the solstices and slowest at the equinoxes. Clocks and watches, however, measure time at a steady rate, known as mean time, while solar time fluctuates as mentioned above – the equation of time is the offset between mean time and solar time.

Equation of Time Settings | Design Considerations | Equation of Time Functionality

Equation of Time Settings

eq: {
    id: string;
    range: {
        max: number;
        min: number;
    }
}

id | Required

The DOM element ID of the Equation of Time hand or disc.

Props	Required	Type	Default	Value(s)
id	Yes	string	-	DOM Element ID

range | Required

With the Equation of Time indicator drawn at 0, define the minimum and maximum rotation values in degrees for the indicator.

Props	Required	Type	Default	Value(s)
range.max	Yes	number	-	The maximum rotation value when the equation of time value is positive.
range.min	Yes	number	-	The minimum rotation value when the equation of time value is negative.

Design Considerations

When designing an Equation of Time display to work with Horologist, there are a few considerations to keep in mind.

1. The Equation of Time indicator should be drawn at the 0 value of the display, with a maximum range of 16 minutes and minimum range of 14 minutes.
2. Horologist does not assign any transition-origin properties. These must be defined manually.

Equation of Time Functionality

The Equation of Time value can range between of a minimum of 14 minutes and a maximum of 16 minutes. These values are then divided against the range.min and range.max values to determine the rotation value to apply to the indicator.