We sympathize. You need your Starbucks coffee and you need it now, either so you can get a jump on your day and rediscover what it feels like to be human or to just sit in your local coffee shop for 18 straight hours. People have been known to sit in their Starbucks come hell or (very) literal high water, after all.
So here's the scoop. In larger cities, Starbucks locations open around 5 a.m. to capture the weekday morning rush, but specific times may vary by location, especially in smaller cities, with some opening as late as 7 a.m. On weekends, locations generally open later, with some opening as late as 9 a.m. Same goes for holidays; individual store managers have discretion on deciding when they'll stay open.
For Starbucks closing times, it's the same deal. Individual locations decide their hours, with larger cities like New York staying open until 11 p.m. and smaller cities only staying open until 6 p.m. or so. Because it's so case-by-case, it's a great idea to check the Starbucks store locator, which will list times for individual coffee shops.
Whatever you do, when you get there, just make sure you order something terrific off the menu.