40th Birthday T Shirt. I'm Not 40, I'm 18 with 22 years experience. Do you have a friend who is having a hard time accepting that he is now over the hill? Make him laugh and loosen up by getting him this 40th birthday t-shirt. It’s a white shirt that says “I’m Not 40, I’m 18 With 22 Years Experience”. He will certainly get a kick out of it. The number “40” is in white with cracks showing through on a black background. The rest is in black ink with a red outline. This funny 40th birthday shirt makes a terrific 40th birthday gift! It is made of 100% cotton that is already preshrunk so it won’t ever get ruined. This 40th birthday shirt is available in medium, large, extra large and extra extra large. Help your friend get over the fear of his age and be able to laugh about it! He will appreciate your support and thought!