at a time or at the time از کدام و کجا استفاده کنیم؟

‘At a time’ refers to now: اشاره به اکنون داره

At a time when there are so many people unemployed you have to take any job you can get. 

or the future. و یا اشاره به آینده

We could meet at a time that suits you. 

‘At the time’ refers to the past. اشاره به گذشته دارد

At the time I was young and foolish.