If you get ill during a month period, and it recurs annually, then your sub-conscious is trying to tell you something. Either mental imagery or hypnosis may find it, then again, it may not. Either way though, it is still within your brain and you actually do control it.

You must also be careful in trying to forget dates, because all that does is reinforce to your sub-conscious that x date is coming around. If you are at peace with the pain any date, month or the like gives, there is really no real need to get ill at that period, however; some things at the sub-conscious may just be out of your control and you have to live with that one.

Those focused on the belief though that they must, or should get ill on a certain date each year.... nonsense. The faster you forget specific dates the better if you get ill upon them. I have no idea nowadays what my brothers date of death was. I couldn't even tell you specific dates of trauma as their where so many, though that is my trauma which is military related and vastly different from isolated trauma.

Point is though, is that there is no need to become ill on any specific date just because your trauma occurred on that date years prior or the like.

If you want to actually get specific, if you look at the perpetual calendar model, the actual same date each year isn't actually the same in time as we have leap years and so forth attempting to balance time itself. It is purely a date, though not the date of your trauma itself, as that can only occur once, being the day it happened. It technically cannot be relived unless you can travel back in time, which means you control whether you take specific notice or not of that date in future years.