How to get tooltip to show year only

My notebook

My year is stored as new Date(1990, 0). x-axis ticks are formatted correctly (1990). However, tip year are formatted as 1990-01-01T08:00Z. Is there any way to have tip just show year?

I’m changing my notebook frequently, so here’s a screenshot.

You can specify your own channels (and override existing ones):

  tip: true,
  channels: {
    "Start year": d => d3.utcFormat("%Y")(d.Date),

Thanks, that worked.