op-neg-output: those input tiddlers in which field <<.place F>> is at least <<.place D>> days in the { future | past }
op-output: those input tiddlers in which field <<.place F>> is <<.place D>> days in the { future | past } or any time { before | after } that, including { past | future }
op-parameter: a number of days, defaulting to 0 { positive | negative }