One Operation can be executed in several time periods. It is possible to assign an urgency or timeliness value to each period. Apart from AbsoluteTiming, it is possible to specify a RelativeTiming. One can specify, for example, that a certain fertilizer gift has to be done three to two weeks before planting. Apart from AbsoluteTiming, it is possible for Tasks and Jobs to specify one or more TimeFrames. AbsoluteTiming has a more agronomical meaning, while TimeFrame has a more (machinery) management meaning.