http://www.grammaring.com/changes-in-place-time-and-person-in-indirect-speech

No changes are made to words referring to place, time or person if we report something at the same place, around the same time, or involving the same people:

John: I’ll meet you here.
John said he would meet me here.
 (reported at the same place)

Alison: My train leaves at 9.30 tomorrow.
Alison says her train leaves at 9.30 tomorrow.
 (reported on the same day)

Richard: I can help you, Stephanie.
I told you I could help you.
 (reported by Richard to Stephanie)
I told Stephanie I could help her. (reported by Richard to a third person)

Changes are made if there are changes in place, time or people:

John: I’ll meet you here.
John said he would meet me at the café.
 (reported at a different place)

Alison: My train leaves at 9.30 tomorrow.
Alison said her train leaves at 9.30 today.
 (reported on the next day)

Richard: I can help you, Stephanie.
Richard told me he could help me.
 (reported by Stephanie)
Richard told Stephanie he could help her. (reported by a third person)
I told Stephanie I could help her. (reported by Richard to a third person)

The following table shows some typical changes of time expressions in indirect speech. Remember that the changes are not automatic, but they depend on the context:

direct speech indirect speech
now then / at that time
tonight last night, that night, on Monday night
today yesterday, that day, on Monday
yesterday the day before / the previous day, on Sunday
last night the previous night / the night before, on Sunday night
tomorrow today, the following day, on Tuesday
this week last week, that week
last month the previous month / the month before, in June
next year this year, the following year / the year after, in 1996
five minutes ago five minutes before
in two hours’ time two hours later