Mori Tower Observation deck

I am kind of scratching my head right now with information that I have for the Tokyo City View observation deck at the Mori Tower in Roppongi.

On the Japan Guide page it gives the hours of operations and no information on days closed. Whilst on the Roppongi Hills website it gives the hours of operations for Weekdays, Saturdays and days preceding holidays. However I can't find any information for Sundays..

I have contacted them and I was referred to the website that I already know about and no mention of whether it is open on Sundays. So I am wondering whether the Observation Deck is open on a normal Sunday?

Thank you to anyone who can answer this question.

It is a really badly localized website! Sundays are considered "holidays".

Thank you Uji for your response.

So I can stick with the Sunday for my visit then?