Just so I'm sure, if the day IS Thursday, you would reply with "Jo", as it's a negative question?
Yes, that's right. Jo, det är det would be the correct answer to this one.
finns is more like 'exists', and we don't think of days of the week as something that 'exist', more like something that 'goes on', and then är is the suitable verb. It's the same with other time periods like years, seasons etc., like Det är vinter 'It is winter'.
I just want to notice an error. In todays swedish both idag and i dag are correct. I dag is more classical but idag is more popular. Cheers from sthlm
The slowed-down pronunciation of this was very confusing, mostly with "torsdag" ... usually I can hear better when I use it but this time the regular one was much more helpful.
A lot of the names of the days of the week got their name from the Norse... Wednesday is Odin's day, Friday is Freyja's day... There might be another, but those 3 I know of...