Yiddish: I care like a cat cares if it's Wednesday.

I don't care at all.  It doesn't concern me.  (see also)  
SOURCE: Stutchkoff, Der Oytser fun der Yidisher Shprakh.  (image source)  Compare:

Es art mikh vi der farayoriker shney.  |  .עס אַרט מיך ווי דער פֿאַראַיאָריקער שניי
It bothers me like last year's snow.

SOURCE: Stutchkoff, Der Oytser fun der Yidisher Shprakh

עס אַרט מיך ווי די קאַץ פֿון מיטוואָך.

Es art mikh vi di kats fun mitvokh.

I care like a cat cares if it's Wednesday.