Snap the package — and the harvest or best-by date if it's on another side. Freshie reads what's printed and tells you how fresh it is and how to brew it.
Try Freshie AFBETA— autofocus scanning: point at a shelf, a menu, or what you're holding
Front of the package
Where the date is printed
Add either or both — two photos give the most accurate read.
Green and lightly oxidized teas fade fastest — a harvest date matters most there. Well-stored oolongs, blacks, and pu-erh keep far longer.