How do you know when a penny was made?

Answer 1

Most coins have a date. Almost all coins are minted in the same year they are dated, but there are a few exceptions. If the date is worn off, I could give you a range of possible dates if you can give a good description of the design. BTW - the Penny is a British coin. The US uses Cents officially (but even the US Mint is calling them pennies now).