^It's true. SDC is in its 51st year of operation this year. They've been open 50 years and so many months.
Dollywood has been open 24 years and so many months, so they are technically in their 25th year of operation.
This is an odd way of looking at things. For example, we don't look at it this way with personal birthdays and anniversarys. I turned 27 last month, which means I'm technically in my 28th year (I'm 27 and two months old); I haven't completed my 28th year yet. I suppose we personally don't look at it this way because we only celebrate the actual day; it's not a year-long celebration.
For companies/corporations, they tend to have year-long celebrations, so then it gets tricky. Do you celebrate the anniversary during the anniversary year or after the year is completed? It gets even more tricky when you take into account the exact day of the anniversary; most companies/corporations just do it by calendar/operating year rather than kicking it off on the exact day.
It's just personal preference, I guess. SDC decided to celebrate it after the operating year was completed, while DW decided to celebrate it during the actual operating year. Nothing wrong with either approach; DW isn't the only company that's celebrated an anniversary during the anniversary year rather than after it's completed. I've seen it done before.