一般地，直接引语变间接引语时，时态要发生变化；然而，时态不变的情况主要有：

1． 若直接引语表述的是客观事实、科学真理和格言时。如：

The teacher said, “The earth moves round the sun.”

→The teacher said that the earth moves round the sun.

The old man said, “There are twelve months a year.”

→The old man said that there are twelve months a year.

2． 若直接引语所表述的事在目前和说话时同样有效时。如：

He said, “I am a man, not a woman.”

→He said that he is a man, not a woman.

She said, “I like playing football.”

→She said that she likes playing football.

3． 若直接引语为一般现在时，且表示反复出现或经常性、习惯性的动作时。如：

Tom said, “ I have lunch at school every day.”

→Tom said that he has lunch at school every day.

4． 若主句的时态是一般现在时、现在进行时或一般将来时时。如：

He often says, “I will never forget you.”→He often says he will never forget me.

He will say, “I have done my best.”→He will say that he has done his best.

5． 若直接引语是过去完成时。如：

The girl said to her mother, “I had finished my homework before supper.”

→The girl told her mother that she had finished her homework before supper.

6． 若在当天转述别人的话，且直接引语中含有明确的表示过去的时间状语时。如：

Lily said to me, “I was late for class yesterday.”

→Lily told me that she was late for class yesterday.

7. 若直接引语中含有when, since, while等引导的表示过去的时间状语从句,变间接引语时,从句时态不变。如：

She said, “I went there when I was six years old.”

→ She said she had gone there when she was six years old.

8. 若直接引语的谓语中含有would, should, might, must, used to, ought to, had better等动词时。如：

She said, “We should help each other.”

→ She said we should help each other.

9. 若对刚说过的话马上转述时。如：

Jim: I have been a teacher.

Lucy: What did Jim say?

Tom: Jim said that he has been a teacher.