I doubt any pet stores are open today. What are you needing? I'm sure Wal-mart is open, and Walgreens. We even have one chain of grocery stores open here. But most everyone else allows their employees to have the day off.
One of the malls here is opening at 12:01 am - but they don't have a pet store, just a little kiosk, and I don't know if the kiosk are opening. Two of the department stores at this huge mall aren't even opening until like 5 or 6 am.
If you just want to buy things & don't need them immediately, there is always the internet - open 24/7