they have their own calendar

One of the ridiculous charges against Chabad that was stuffed in my face early on was that they went against Klal Yisroel by having their own calendar. But they don't have their own calendar. 5th of Sivan is the same for Chabad as everyone else. They didn't make up their own months. They use the same months. 7th of Nisan is 7th of Nisan. What they do is count their yearly Tanya schedule from 19 Kislev.

And what about Daf Yomi? That doesn't start on Rosh Hashana. Here's when it starts:

What's that? Teves. They make their own calendar! But that's just the 14th cycle. Here's the 13th. 

Wait, does it start in Teves or Av? Imagine if Chabad did this. They'd be accused of trying to confuse people.  Every cycle the Daf Yomi makes a new schedule. The 17th cycle will start in Nisan. 

At least Chabad sticks to the same schedule.