This month wasn't a very good one for me.

This month hasn't been a very good one for me.

He wrote three letters today.

He has written three letters today.

We already saw the new Production Manager.

We have already seen the new Production Manager.

They didn't come to class yesterday.

They haven't come to class yesterday.

Did you ever see the Taj Mahal?

Have you ever seen the Taj Mahal?

I worked here for three years (and I still work here now).

I've worked here for three years (and I still work here now).

I didn't see him at work yesterday.

I haven't seen him at work yesterday.

Did you read that article about e-recruitment last week?

Have you read that article about e-recruitment last week?

Did you apply for a job online yet?

Have you applied for a job online yet?

Did you learn a lot in your last job?

Have you learnt a lot in your last job?

Did all the candidates come for interview last week?

Have all the candidates come for interview last week?