There is a convenience function datetimeticks for manual ticks for timeseries, see eg How to plot more ticks in AlgebraOfGraphics or Makie? - #2 by icweaver or Format date axis. The main downside is that you have to select manually on which dates to have a tick.
You’re right that it would be helpful to have a function to just update the formatting, without changing the tick selection. Unfortunately, at the moment that’s hardcoded here, but there definitely should be an API to customize it. Feel free to open an issue about this, so that it’s easier to keep track.