Continuous Timeline (Color) style can be used when you are just trying to symbolize based on a single date/time attribute. This style will produce a color ramp and give you two theme options—New to Old and Before and After. New to Old will symbolize your data chronologically from old to new. You can also flip the color ramp by clicking on the Invert button so that you can symbolize New to Old. The other theme you can use is Before and After, which focuses on one date specifically and use a diverging color ramp to show dates above and below it.