求翻译：暑假即将开始，安排去旅行，为了做好安排，定于今天下午四点半，定于301室召开回忆，教师也来参加，请准时到会。是什么意思？

Summer vacation is about to begin, to travel arrangements, in order to make arrangements, 4:30 P.M. will be held today, be held in Room 301, memories, teachers have to attend, please take the meeting.