This old French postcard has greetings for both Easter and April 1. The left side of the card has the words Joyeuses Pâques (Happy Easter) and an Easter egg. The right side has the words Premier Avril (First of April) and a fish. “April fish” is a tradition in France and some other countries. The tradition includes attempting to attach a paper fish to someone’s back without being noticed.
The postmark on this postcard appears to be 30 – 3 07. Easter fell on March 31 in 1907, so it would have been appropriate to combine greetings for Easter and April 1.