Why would MasterCard issue me a new card a year before the expiration date?

There are two very probable reasons:
1. They changed the terms and conditions on you.
or
2. You’re getting new EMV (Chip & Pin) security built into your card.

If they changed the terms and conditions – this has happened to me a few times before. They probably sent those new terms (aka: the “features” of the card) in a separate letter that looked like junk mail (it didn’t come with the billing statement and hence would be easy to filter out and toss…) a few weeks back.
This happened to me a few times—once with Chase Visa (because of the credit legislation passed in 2010 and enacted in 2012)—Chase got really crafty and switched us over to a “business” account (a sneaky way of preventing us from getting consumer protections)—without explaining why they were doing what they were doing.

US Bank also sent us out new cards inexplicably…just about 6 months before our cards were set to expire. We soon found out why though—they later sent a letter saying they were no loner going to provide “Perk” Points with their Visa Debit card. The letter informed us by accepting the new card we’d accepted the new terms (ceasing to earn points on our card)—which was very crafty because they sent the letter AFTER sending the card..and the card is both our Debit/ATM card and our visa. So..by accessing my money in my accounts with the card I’d already accepted. Then they told us we had to use all our points in less than 30 days, too..because the program was going away. <sigh>

A more benign possibility (#2 from above) is that your cards are by WellsFargo or another lender that is embedding the new chip & pin technology (which is widely used elsewhere in the world and is more secure). Article about EMV here.

Is it the same color? Were you possibly upgraded in some way? But, you would think it would be accompanied by an explanation if you were upgraded. I would call and ask.

It looks exactly the same except for the start and end dates and the security code number. The note about perks does not say they are new and whether they are an upgrade or a downgrade or anything else.

I am automatically suspicious of everything a CC company or a bank does, but I suppose it’s possible that it’s perfectly benign.

I bet this is their way of letting you know that you can use their card instead of any other cc you may have. Puts their card on top in your wallet.

Take it from someone who used to work in that industry, it could be as simple as a clerical error – someone pushes the wrong button and issues you a new card without realizing it.

Call them and ask if this is a mistake.