Since last update, the game no longer pops up a claim confirmation window when the new day starts, nor when the Rewards screen is opened. To claim the daily reward, one must manually tap/click on today's square and 'claim'. I assume that if this is not done, that day's reward is not claimed and is lost forever. Or it stays lit until the end of the month.
Either way, this is an unannounced change from previous behavior, and is likely to catch people off-guard. Also I'm not sure if this change is intended, and if it's contributing anything positive to the UI.
EDIT: In addition, there is no change in the UI after the reward is claimed. I am not sure how it was before, but previous days have big green tick marks. I'm noticing that the tile stays lit and clickable to offer a VIP upgrade. I suspect that whoever made this change didn't design it properly.