How to remove "calendar events" from the lock screen?
On the lock screen swipe left so that there's a big + sign on the screen (or maybe another widget) and then scroll back to the calender so that it's now full screen. Long press the calender and drag it to the top of the screen to remove it.

On my phone the clock was automatically re-added to the lock screen after this but if it isn't then go to the lock screen, swipe till till you see a big + again. Click on this and from the menu of widgets that appears select the digital clock.