Since neither lie on Sundays, Kerry is lying today, and so must tell the

truth on Saturdays, which means Kerry lies on Mondays, Tuesdays and

Wednesdays, and today is one of these days.

So when Kelly says I will lie tomorrow she is telling the truth as the

twins never lie on the same day.

So the day you seek is a day on which Kelly tells the truth (one of

Sunday, Monday, Tuesday, Wednesday), but will lie on the next day

(one of Thursday, Friday, Saturday).

RonL