How time flies!
时光飞逝。
例句
1.How time flies! It's three months since we last met.
时间如梭！自从我们上次见面已经三个月了。
2.How time flies! The four-year college life comes to an end finally.
时光飞逝，转眼间四年的大学生活即将结束。
3.How time flies! We already far away from our childhood.
时间飞逝！我们已经远离孩提时代了。
4.How time flies! We have been far from our childhood.
时间如梭！我们已经远离孩提时代了。
5.How time flies! A week has passed in the twinkling of an eye.
时间过得真快！转眼间一个星期就过去了。