Hm, another oz/vega list question: I want to parameterize the x axis, which is datetime, and I want to add a slider. How do I do this? e.g. what do I put in the step?

:params [
     {:name "lowTime"
      :value "datetime(2021, 02, 18)"}
     {:name "hiTime"
      :value "datetime(2021, 02, 20)"
      :bind {:input "range" :min  "datetime(2021, 02, 15)" :max "datetime(2021, 02, 22)" :step "datetime(0, 0, 1)"}}
     {:name "lowTemp"
      :value 20
      :bind {:input "range" :min 1 :max 100 :step 1}}
     {:name "hiTemp"
      :value 80
      :bind {:input "range" :min 1 :max 100 :step 1}}
   ]