Grandparents Day is September 13th – Flowers Make Us Happier and Live Longer Posted on September 1, 2015Reading Time: 1 minute Minutes | First View Research shows that a small dose of nature, like flowers, can do a world of wonder for our well-being as we age. Wondering when Grandparents Day 2015 is? It’s Sunday, September 13th! So don’t wait to order a beautiful floral bouquet for Grandparents Day now! Port Chester Florist has all types of flowers from modern arrangements, traditional roses, andplants!