It's not Fool's Day yet in any part of the world
We've got to much Fool's Day

A = C B = D C = E D = F E = G F = H G = I H = J I = K J = L K = M L = N M = O N = P O = Q P = R Q = S R = T S = U T = V U = W V = X W = Y Y = A Z = B
Here's a test to see how well you know the code: What does this spell?
Fynnw Ynpgj Dmmj'q Byw!

It's a basic ceaser shift cipher, each letter within the ciphertext is two letters down from its plaintext equivalent...
(And same to you isaac ;D)

A = C B = D C = E D = F E = G F = H G = I H = J I = K J = L K = M L = N M = O N = P O = Q P = R Q = S R = T S = U T = V U = W V = X W = Y Y = A Z = B
Here's a test to see how well you know the code: What does this spell?
Fynnw Ynpgj Dmmj'q Byw!
happy april fools day

Here is a way to crack it:
Modular conversion, encoding and encryption online — Cryptii
lol I was lucky there was an ad before and quickly Xed out
If you search up Cryptii it is actually real tho
There's 55 of them!