X Axis Timestamp format in Bar Chart + Thresholds not working

I have a dataset is timeseries, although it has a quite irregular, hence I decided to use Bar Chart instead of Time Series. There are two issues i am currently facing and hence the questions:

  1. How to change timestamp format on X Axis? Currently HH:MI is shown, but I would like to change it to YYYY-MM-DD. At source, this column has the following format: YYYY-MM-DD HH:MI:SS. I tried using Transform → Convert Field Type but it did not worked for Axis.
  2. How exactly Thresholds work there? I have setup two threshold, but the bars are not properly colored.