I always know when it's the holiday season, or tax time, because so many visitors reach Gillette on Hillsborough by searching for local post office information.
You can find a lot of this information at www.usps.com, and you can even search for all the post offices in a given radius, like I did here.
Here are the business hours for all of the area post offices as given by the USPS web site.
HILLSBOROUGH Mon-Fri 10:00-5:00pm Sat 9:00-2:00pm
BELLE MEAD Mon-Fri 8:00-7:00pm Sat 8:30-4:00pm
FLAGTOWN Mon-Fri 7:00-4:30pm Sat 7:00-12:00pm
NESHANIC STATION Mon-Fri 8:30-4:45pm Sat 8:30-12:00pm
SKILLMAN Mon-Fri 7:00-4:00pm Sat 7:00-12:00pm
BLAWENBURG Mon-Fri 7:15-12:00pm and 2:00-4:30pm Sat 9:00-12:00pm
EAST MILLSTONE Mon-Fri 8:30-12:30pm and 2:30-5:00 pm Sat closed
ROCKY HILL Mon-Fri 8:00-4:30pm Sat 9:00-12:00pm
MANVILLE Mon-Fri 9:30-7:00pm Sat 10:00-4:00pm
RARITAN Mon-Fri 9:00-7:00pm Sat 9:00-4:00pm
SOMERVILLE Mon-Fri 8:30-7:00pm Sat 9:00-4:00pm