The Mexican state of Quintana Roo will move clocks ahead one hour tonight at midnight and be the same as Eastern time year round. This will include Cancun, Riviera Maya, Playa del Carmen, Cozumel, Isla Mujeres, and Tulum. The move is designed to put the region on the same time as the big tourist markets on the US East Coast. From what I've read, local people hate the idea, but the tourism industry pushed this through. You get an added hour of light in the evening, but it'll make for darker mornings.

abcnews.go.com/Travel/cancun-change-eastern-standard-time/story?id=28589197

If you've got flights coming up, check and recheck the schedules carefully, as your arrival or departure times might have to change to accommodate this. It depends on how long ago you bought your tickets.

Will Campeche and Yucatan states follow suit?

No, as it stands now for Yucatan and Campeche states.

There's also some uncertainly about whether or not Q.Roo will observe Daylight Saving Time, like most of Mexico does. Some sources say it will; others say it won't. If it does not, then it would be the same time as NY for four months a year, and the same time as Chicago for the rest of the year.

Something everyone planning day trip to Merida, Valladolid, and Chichen Itza should keep in mind then. Seems like a bad idea for only 1/3 states in the Peninsula to do this.

Since many visitors to C.I. arrive as a day trip from Cancun and vicinity, yes, they'll change time zones. They'll gain an hour heading west and lose it again going back east.

I was in Valladolid about three months ago. I hadn't been there in a few years. Tourism has really grown, and I'd forgotten what a gem of a place it is.