Hi, I saw a line of words explaining the usage of "used to" in my grammer book which says:

....Used to is not used simply to say what happened at a past time.

I worked very hard last month. (O)

I used to work very hard last month. (X)

And that is what the book says. However, I saw another sentence which does use "used to" with a past time:

He used to live here in 1944.

If the above example is correct, then why is "I used to work very hard last month." incorrect? What is exactly the difference of these two examples?

Please give me your opinion and I'd appreciate it.
'Used to' is used to refer to regular or habitual past activiites or states. I'd say that the main problem is that limiting 'work hard' to 'last month' suggests that 'work hard' was not a habitual or regular past activity.
Yeah, I think a month is too short a period of time, and it's fixed. I think used to is used when the time frame doesn't sound too fixed or determined.

I used to live there from 1998 to 2002. <-- Doesn't sound ok to me. Is it just me?
I used to live there in 1998.
<-- I lived there in 1998, but that was not the only year I was living there.
I used to live there when I was still with Sarah. <-- Ok.

That's what it seems to me... Emotion: smile
Students: We have free audio pronunciation exercises.
KooyeenI used to live there from 1998 to 2002.
That might be used since the period of time is substantial -- especially if the time frame is added as an afterthought.
Yankeeespecially if the time frame is added as an afterthought.
Hmm, but that underlined might, and the part I just quoted tell me that that example might be borderline acceptable, and that my intuition was not that wrong after all. Right Amy? Emotion: smile
On the other hand, my intuition tells me that the more I think about that sentence, the more I feel dizzy, LOL. Seriously, I think I had better forget about it... because on second thought, my intuition is now telling me that that sentence is acceptable in the right context, where the focus is not on the period of time. Emotion: smile
Hi Kooyeen
Yes, I think your intuition was good.
One of the reasons I didn't like the use of 'used to' with 'last month' is that the time frame sounds much too limited to be considered habitual. It also sounds as though it was only one month out of many months (i.e. it sounds more like an exception than the rule).
When people use 'used to', the time frame usually isn't too specific in terms of months or years. It tends to be used more often with expressions such as 'when I was young', 'when I lived there', etc.
Site Hint: Check out our list of pronunciation videos.
Thank you! I understand now. What Amy said is very helpful, because all my grammar books weren't able to explain this as clearly as Amy.