ROS 2 (timer) callback execution order

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I'm working on a node that has several timers which are operating with the same frequency. They are in the same callback group and executed by a SingleThreadExcetuor. I can't find any documentation on the ordering in which the callbacks are exceuted. Is this random or in order of timer creation. Moreover, is there any option to keep the timers on the same frequency but provide a little offset, meaning a timer has the same frequency but 0.01 s later than the other one?