What someone has told us belongs to the past, because the situation may have changed:
That is why we use the past tenses when we report what somebody else has told us (the past progressive instead of the present progressive etc.).
Of course Jenny has got her own past. The past simple can change into the past perfect - perfect tenses indicate that one thing happened before another thing:
The past simple can remain unchanged, but only if the meaning doesn't change:
In this example we have to change the tense:
The past perfect tenses remain unchanged.
Jenny has also got her own future. The future tenses change into the future in the past (will changes into would):
Other words also change in reported speech:
Other changes include:
All modal verbs can be used in direct speech, but only the modal verbs in the right bubble can be used in reported speech - they change as follows:
Additionally, must can remain unchanged, but can also change to had to when it expresses obligation. The modal verbs in the right bubble don't change in reported speech, just like modal perfects and the past perfect tenses.