Aren't there two ways of putting a sentence with an i-adjective into past tense? かった and でした?


今日ヨガは最も難しいことです。

>   1. 今日ヨガは最も難しかったことです。
>   2. 今日ヨガは最も難しいことでした。
>

Are both sentences correct? What are the different implications? I haven't
worked with 最も yet, I would try to use 一番 here instead. What I perceive as my
problem is かった or でした. Please, point out all the things.

今日一番難しいことはヨガです。

>   1. 今日一番難しかったことはヨガです。
>   2. 今日一番難しいことはヨガでした。
>




I believe the most natural ways to phrase your sentence are as follows:

> 今日はヨガが一番難しかった（です）。  
>  ( Out of all the activities I did today, ) Yoga was the most difficult.  
>  _Note: emphasis is on the word "yoga". です can be added but is not
> necessary._
>
> 今日一番難しかったのはヨガでした。  
>  Today the most difficult part was Yoga.  
>  _Note: の can be replaced with こと, they are interchangeable._
>
> 今日のヨガが一番難しかった（です）。  
>  ( Out of all the yoga I've done, ) Today's yoga was the most difficult.  
>  _Note: emphasis is on the word "today"._

In general, 一番 and 最も are interchangeable, however 一番 indicates an explicit
number one ranking, whereas 最も does not necessarily indicate a number one
ranking when referring to a group, just like the word "most".

> 彼はクラスで一番頭のいい生徒の一人です。✘  
>  彼はクラスで最も頭のいい生徒の一人です。✔  
>  He is one of the most intelligent students in his class.




I believe the most natural ways to phrase your sentence are as follows:

> 今日はヨガが一番難しかった（です）。  
>  ( Out of all the activities I did today, ) Yoga was the most difficult.  
>  _Note: emphasis is on the word "yoga". です can be added but is not
> necessary._
>
> 今日一番難しかったのはヨガでした。  
>  Today the most difficult part was Yoga.  
>  _Note: の can be replaced with こと, they are interchangeable._
>
> 今日のヨガが一番難しかった（です）。  
>  ( Out of all the yoga I've done, ) Today's yoga was the most difficult.  
>  _Note: emphasis is on the word "today"._

In general, 一番 and 最も are interchangeable, however 一番 indicates an explicit
number one ranking, whereas 最も does not necessarily indicate a number one
ranking when referring to a group, just like the word "most".

> 彼はクラスで一番頭のいい生徒の一人です。✘  
>  彼はクラスで最も頭のいい生徒の一人です。✔  
>  He is one of the most intelligent students in his class.

