Hi,
Thanks for your suggestion, I can definitely see how that would be more convenient. Unfortunately, keeping an in-game event calendar up to date would be quite difficult. The patcher/web version is generally more effective, as it allows us to make instant updates with a single click, whereas updating an in-game calendar would likely require maintenance(s) every single time. While there may be possible workarounds, implementing them would take considerable time & effort. Since the current calendar functions well already, and there aren't any game altering issues around it, we’d prefer to allocate our time and resources to other priorities.
Warm wishes,
Essence.