Usage of ました form and た form with こと


Example: Is the formal of にほん に いった こと が ありまづ this : にほん に いきました こと が ありまづ. Or
is the first one used in both cases?




> **V-た form + ことがある** is the formula to say about past experience of doing
> something

In にほん に いった こと が あります  
It's already formal since the ある is written as あります。 **You cannot change the
いった to いきました** when using this pattern。It should only be V-た form. And note
that ある in the end cannot be changed into past form あった since you still have
the experience until now.




> **V-た form + ことがある** is the formula to say about past experience of doing
> something

In にほん に いった こと が あります  
It's already formal since the ある is written as あります。 **You cannot change the
いった to いきました** when using this pattern。It should only be V-た form. And note
that ある in the end cannot be changed into past form あった since you still have
the experience until now.

