what is time expression and where is it used

Dear student 

Time expressions are used at the beginning or at the end of sentences, to denote a certain tense or time during which the event mention is occurring. 

For example:

Nowadays, everyone prefers to use the email.

Some examples are -

Present
- Nowadays, these days, recently.

Past
- Ago, since, recently, last week/day/night/month. 

Future
- Soon, by the time, next week/month, in the following week/month.  


Regards