The following is currently happening on the very latest mainline Chrome 80.0.3987.116 (Official Build) (64-bit):
Whenever I visit the Calendar (/plan), it displays January 2020, even though it’s now February. Also, if I select a month and year then click Go, the calendar displays the month before the one I selected - e.g., select April 2020 and get March 2020, select August 2022 and get July 2022. I suspect that the two bugs are really the same one.