I say, and with God's help: His ablution is invalidated by the end of the time, not by the beginning of the time. Attributing the invalidation to the exit and entry is metaphorical, for the invalidating factor is the previous event, and its effect is in this time. Refer to: Umdah al-Ri'ayah 1: 135, and Fath al-Qadeer 1: 161, among others, and God knows best.