They had a good sleep of a few hours without their noticing it, until the east was already beginning to grow bright. 他们睡了好几个小时,不知不觉,东方已破晓了。
Three months have passed before we knew it. 不知不觉已过了三个月。
牛津高阶第八版
美国韦氏词典
Dictionary.com
Free Dictionary
维基百科 (自由的百科全书)