My mum says:
You have to go back home tomorrow by 6pm.
The day after, do I tell my friend:
My mum said I have to go back home by 6pm
OR
My mum said I had to go back home by 6pm
Another example: my mum says
I think it is a good chance for you.
Next day after, do I tell my friend:
My mum thought it is a good chance for me.
OR
My mum thought it was a good chance for me.
When I repeat the past conversation by using "(someone) said", is it a must that I need to change the sentence to past tense, or can I keep it in present tense?