Indeed, the first card. Wikipedia:

The first Christmas cards were commissioned by Sir Henry Cole and illustrated by John Callcott Horsley in London on the 1st of May 1843.

The central picture showed three generations of a family raising a toast to the card's recipient: on either side were scenes of charity, with food and clothing being given to the poor. Allegedly the image of the family drinking wine together proved controversial, but the idea was shrewd: Cole had helped introduce the Penny Post three years earlier. Two batches totaling 2,050 cards were printed and sold that year for a shilling each.

Commissioned in May, yes, but I'll bet they still went out the last week before Christmas. You know how that goes.