Nothing wrong, just got amnesia.;) But seriously speaking and most probably, you have been overworked yourself a bit. Just try to take a big rest and stick some calendar on the wall. That's all so far,what a doctor prescribes.

Time to take some lucidril! :P Just kidding!!!! In case you don't know what lucidril is: It is an anti-aging drug widely used by humans to increase brain energy, since it stimulates the chemical activity of the brain.

Just be calm my dear friend. Nothing wrong with you actually. This kind of situations happen when you are tired, not enough sleep or worried something. Good memory is important to everybody. It is an essential part of intelligence. Most people need good memory – in schools, in the work sites, and even at homes. There are various reasons why people become forgetful. The following are some of the reasons or causes of forgetfulness: senility, alcoholic drinks, unbalanced diet, wrong lifestyle, diseases, lack of exercise, and accidents. As we grow older, we tend to become more forgetful. This may be due in part to the acceptance as truth of the conventional belief that almost all old people become forgetful.This may be due to the slowing down of the myriad of processes in the human systems as people grow older. But this belief system is reversible. People can be old and still have sharp, retentive memories. Drinking liquor and other alcoholic drinks is very harmful to the brain. Thousands of brain cells die permanently during every drinking bout, and they are irreplaceable. The brain thrives mostly on glucose, a sugar found naturally in honey and sweet fruits. This sugar can also be made artificially from carbohydrates by hydrolysis. For a brain to function excellently, it must be feed with food rich in glucose such as fruits, nuts, grains, and vegetables. Avoid flesh meats, milk, and sugar. They destroy the memory. You may wonder why milk and sugar are not good for memory. Milk and sugar combination is not good for memory. When sugar (not from fruits) are taken into the body, the pancreas is stimulated to secrete insulin to neutralize the excess sugar in the bloodstream. This causes a temporary deficiency of sugar, thus starving the brain of needful glucose. Animal flesh meats are saturated with harmful chemicals, such as growth hormones and feed additives. They also contain stress hormone called 17-hydroxycorticosteroid that blocks the neurotransmitters to the brain. Animal products have chemicals or substances that have mind-altering effects such as thyramin in cheese; tryptamine in fish and sausages, and arachidonic acid. Junk foods and carbonated drinks are loaded with excitotoxins such as monosodium glutamate, aspartame, and caffein that are detrimental to the brain. Staying late at night, and other forms of insomnia impair the memory, Accidents and diseases too can destroy the memory. And most off all, lack of exercise. Regular physical exercise enhances good blood circulation to the brain to supply glucose and oxygen. Most important, the brain must be trained to memorize regularly. Constant practice makes memorizing easier.

It's probably nothing serious. If it gets worse, and you start confusing everything, it would be time to seek help. In your confusion of the days, it seems your mind thinks the work week is/will be longer than it really is. Are you tired of work? Does it seem like it never ends? It could be too much work. It could be CBV (cloudy brain virus). Call your boss and tell him you can't come in because you don't want to infect the rest of the workers with cloudy brain. You are only doing what is best for the company. ; )

Maybe you dont really think about stuff like .. what weekday is it? Or it is not important for you. To make the difference more important you could plan for the week what to do on each day... or have special food that you like on a certain day. If you are generally... well ..out of it at times... you could try to play it off as a joke... a running gag of sorts ^^ Thats what I usually do if I have faults that I cant change, I think stuff like that actually makes a person more interesting.