its because android manages the process of release activities,if you want to finish the previous activity,then add this after start activity:
HomeActivity.this.finish();
either you can you use flag to clear previous activities
eventdetails.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
eventdetails.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
or both:
Intent eventdetails = new Intent(HomeActivity.this,EventDetailsActivity.class);
eventdetails.putExtra("eventId", ev.getId());
eventdetails.putExtra("eventDate", ev.getEnglishDate());
eventdetails.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
eventdetails.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(eventdetails);
HomeActivity.this.finish();
hope it will help to resolve the issue.