Use the left/right arrow keys to change the date
Jump to Dayperiod
(tip: Drag "Jump to Dayperiod" to your bookmarks bar, then click it to jump straight to the day you need)

UPDATE: On 2024-06-17, had some minor code changes. If you use the "Jump to Dayperiod" bookmarklet, you should delete your current bookmark, then drag "Jump to Dayperiod" to your bookmark bar again.