Observe the month shifts as decreasing offsets: $-0, -1, -2, -3, -4, -5, -6, -7$ (in months).

January $- 0 =$ January January $- 1 =$ December December $- 2 =$ October October $- 3 =$ July $\rightarrow X =$ July July $- 4 =$ March March $- 5 =$ October October $- 6 =$ April $\rightarrow Y =$ April April $- 7 =$ September

Hence, $X =$ July and $Y =$ April.