Dru Sefton

Hi, sorry if this has been previously addressed. I live on the West Coast and work the crosswords on my morning and evening commute. But if I return to the puzzle after 4 p.m., it’s often switched to the next day. Grrrr! What time does it advance to the next day? Is there any way to revert to the previous day’s unfinished puzzle? Thanks in advance for any advice.