A system and method for executing a graphical program which has a plurality of timed loops, wherein the timed loops utilize timing sources that are related to or derived from each other. According to one embodiment of the method, a graphical program having a plurality of timed loops may be created. In one embodiment the timing sources may be related to each other according to tree hierarchy. Each of the loops in the graphical program may be associated with one of the timing sources. Thus the plurality of loops may be viewed as a group of loops that are grouped together due to the relationships among their respective timing sources. Execution of the graphical program may then begin. Execution of the loops may be delayed until every loop in the group is ready to execute. After every loop in the group is ready to execute, the timing sources for the various loops may be started. To satisfy the defined relationships among the timing sources, the timing sources may be started in an order based on their hierarchical relationship. Once the timing sources have been started, execution of the loops may be begun such that each loop executes based on its respective timing source, i.e., iterations of each loop are timed by its respective timing source.