YOU SAID:
i am getting a haircut tonight
INTO JAPANESE
今夜は散髪してます
BACK INTO ENGLISH
I have a haircut tonight
INTO JAPANESE
今夜はヘアカットがあります
BACK INTO ENGLISH
There is a haircut tonight
INTO JAPANESE
今夜は散髪があります
BACK INTO ENGLISH
I have a haircut tonight
INTO JAPANESE
今夜はヘアカットがあります
BACK INTO ENGLISH
There is a haircut tonight
INTO JAPANESE
今夜は散髪があります
it is unlikely that this phrase will ever reach equilibrium