Pronunciation of 日 in compound words


I learnt from my teacher that the days of the month from 1 to 10 use kun and
irregular pronunciations:  
一日: ついたち (irregular)  
二日: ふつか (kun)  
三日: みっか (kun)  
...  
十日: とおか (kun)

But for words like 一日目, 二日間 and 三日間後, what would be the correct pronunciation
and the rules for this? I heard 一日目 is いちにちめ and 三日間後 is みっかかんあと. Is this
correct?




Yes, what you've learned is correct. The first ten days "always" (that is,
I've never found otherwise) use the kun readings, except for `一日` as you noted
with `一日目`. Also, for "later/after", the pronunciation is `ご`, not `あと`.

>   * 今日は誕生日の四日前（よっかまえ）です。 → Today is 4 days before my birthday.
>   * 九日間（ここのかかん）かかった台風 → A typhoon that lasted for 9 days
>   * クリスマスの六日後（むいかご）は大【おお】晦【みそ】日【か】です。 → 6 days after Christmas is New Year's
> Eve (Ōmisoka). / The 6th day after Christmas is New Year's Eve.
>




Yes, what you've learned is correct. The first ten days "always" (that is,
I've never found otherwise) use the kun readings, except for `一日` as you noted
with `一日目`. Also, for "later/after", the pronunciation is `ご`, not `あと`.

>   * 今日は誕生日の四日前（よっかまえ）です。 → Today is 4 days before my birthday.
>   * 九日間（ここのかかん）かかった台風 → A typhoon that lasted for 9 days
>   * クリスマスの六日後（むいかご）は大【おお】晦【みそ】日【か】です。 → 6 days after Christmas is New Year's
> Eve (Ōmisoka). / The 6th day after Christmas is New Year's Eve.
>

