Past Simple or Present Perfect

Past simple is used to talk about actions in the past that have finished. It talks about 'then' and definitely excludes 'now'.

Present perfect simple is used to look back on actions in the past from the present. It always includes 'now'.

These sentences are in the past with no connection to the present.

• I first got to know him 10 years ago.
• I started work here in 1989.

These same situations seen from the present.

• I've known him for 10 years.
• I've worked here since 1987.

Time expressions like 'yesterday', 'ago', 'last year', 'in 1999' with the past simple.

• We spoke to him yesterday.
• She joined the company in 1999.

Time expressions like are 'ever', 'never', 'since' with the present perfect.

• I've never seen so many people here before.
• I've done a lot since we last talked about it.