A time then you have crap-load of work to do before the week is over.
three- indicates the immensity of the work
shits- implies the things which need to be accomplished are unpleasant
Wednesday- signifies the urgency of the work to be done
John: Hey, do you want to catch a movie tonight?
Sarah: Sorry, you caught me "three shits from Wedneday". Maybe next week when finals are over.