by the time（到……时为止）
By the time I arrived, the movie had started.
before/after（在……之前/之后）
He had left before I called him.
by + 过去时间点（截至……）
She had finished the report by 9 p.m.
体现“过去的过去”，常与一般过去时搭配使用。
at this time yesterday（昨天此时）
I was studying at this time yesterday.
when/while（当……时，常与一般过去时连用）
She was cooking when the phone rang.
from…to…（从……到……）
He was working from 8 a.m. to 5 p.m.
持续信号词（用于进行时）：
all day/night（整天/整夜）
They were working all day.
yesterday（昨天）
I finished my homework yesterday.
last week/month/year（上周/上个月/去年）
She visited Beijing last summer.
…ago（……前）
He left two hours ago.
in 2020（在2020年）
The event happened in 2020.
just now（刚才）
They called me just now.
always（总是）
usually（通常）
often（经常）
sometimes（有时）
every day/week/year（每天/周/年）
on Sundays（在周日）
频率副词（用于一般现在时）：
sometimes（有时）、often（经常）、seldom（很少）
He often plays basketball after school.
now（现在）
at the moment（此刻）
right now（现在）
these days（这些天）
Look!/Listen!（看！/听！）
already（已经）
I have already read this book.
yet（尚未，用于否定/疑问句）
Have you finished yet?
ever/never（曾经/从未）
Have you ever been to Paris?
since + 时间点（自从……）
She has lived here since 2010.
for + 时间段（持续……）
They have studied for three hours.
阶段性时间（常用于现在完成时）：
recently（最近）、lately（近来）
I have seen her recently.
tomorrow（明天）
We will have a test tomorrow.
next week/month/year（下周/下个月/明年）
They are going to travel next month.
in the future（未来）
Robots will help humans in the future.
soon（很快）
The meeting will start soon.
in + 时间段（在……之后）
The train arrives in 10 minutes.
