Thank you, Kawabata-san,
I can confirm that the Date/Time control does not support displaying Year only in the current Preview release. There is a "Month Year" option. I understand that this is not what you're looking for.
On a related note, you can group data by year using the drop down on the Time field for each layer. When grouped by year, all data for that year will occur together at the beginning of the year.
Even with this data grouping, the Date/Time control will continue to show more granular dates with this release.
I hope this helps!
Blair Neumann (MSFT)
