No special equipment needed. Here's the routine:

1. Check the bag for a 'Roasted On' or 'Roast Date' label. It's usually on the bottom or the back, sometimes in small print.
2. Do the math from that date to today. If it's more than 30 days, put the bag back.
3. When you get home, transfer the beans to an airtight container and keep them out of direct sunlight. Avoid the freezer—it's not your friend here.
4. Brew and taste. If the coffee tastes flat or overly bitter, check the date again. You'll probably find it's older than you thought.

That's it. No pH strips, no refractometers, no subscription to a coffee science journal.