About half of the advent calendars we've had over the years included the 25th and half didn't. The ones that give treats generally do include the 25th. The ones that just reveal pretty pictures generally don't. Those tend to have double doors on the 24th.

I think it might be that the ones I remember from childhood were usually European (German, I think). My mother used to scour stores for them in the 1970s. The ones we've had for Cordelia have all been US produced.