When considering time as a variable which undergoes cycles across a data-series (ex. Month of year across a multi-year time-series, or time of day in a multi-day study), it is often useful to express time on a circular scale. Typically, I see this accomplished with a sine or cosine transformation of the data. While this approach does indeed circularize the data, when a vector of evenly spaced values is transformed, values in the resultant vector are not evenly spaced. How would one best circularize a time vector, but retain the interval spacing between points?