I have this too. Letters and numbers have colors and sometimes smells. Like the letter W is yellow and smells like bananas. G is dark purple and smells like cotton candy. The days of the week, months of the year, decades and centuries are all colored and have a 3D pattern in my brain, as does the alphabet and numbers. The days of the week have always been the same for me. Sunday is pink, Monday white, Tuesday blue, Wednesday yellow, Thursday brown, Friday black and Saturday green. It makes it a heck of a lot easier when trying to figure out, say, how many days ahead something is going to take place. Sometimes pictures, letters, numbers or words have a sound associated with them. Even shapes have colors, like triangles are orange.