The last time we checked, there are only 12 months in a calendar year. Anyone who does some quick math knows that an 18-month olf baby has experienced at least one Christmas, and is about to experience a second Christmas. This is a very cute baby outfit, but unless a one-year-old is a giant, it probably won't fit into this Santa shirt for its first Christmas. That is okay though.
Anyone who buys this shirt can just pretend that their 18-month-old is experiencing Christmas for the first time. As a newborn, they probably don't remember the first one anyways!