You are spot on there Jimtama. What I've done is printed off the Bell Potter (BP) calendar (the most comprehensive one of the three) and then added all of the extra companies included in the other two calendars. I've just added them in by pen on the left side under the date.
I've also noted that there are different dates listed for a couple of companies, for instance - BP has ILU (Iluka) reporting on the 19th, but Commsec has ILU reporting on the 14th. Also, BP has NST (Northern Star) reporting on the 25th, but Commsec has NST reporting on the 31st. In the case of NST, it looks like Commsec are correct, because NST's website states that they will be reporting on the 31st - https://www.nsrltd.com/investor-media/events/
Commsec also look to be correct regarding ILU reporting on the 14th: https://www.iluka.com/investors-media/events
Based on that small sample (of 2), I would assume that the Commsec dates are more accurate than the Bell Potter dates. I've included the Morgans calendar mostly because of their ratings and comments, which can occasionally be worth reading, even if I don't always agree with them. Also, as you correctly point out, there are a small handful of companies in the Morgans calendar that are not included in the others, such as Pro Medicus (PME).