Update documentation to mention events crossing years

Author: wookie184

events/README.md

@@ -23,7 +23,7 @@ start_date: July 10
 end_date: July 20
 ```
 
-There must be exactly 1 fallback event, and 0 or more non-fallback events. Events cannot collide in time, and the end date must either be equal to the start date (1 day event) or chronologically subsequent. Both bounds are inclusive, and the format shown in the example above must be followed.
+There must be exactly 1 fallback event, and 0 or more non-fallback events. If start_date is a later day in the year than end_date, the event is interpreted as starting in one year and ending in the next. Both bounds are inclusive, and the format shown in the example above must be followed.
 
 The markdown section of the meta file then contains the event's description. Descriptions are made available directly in the Discord guild as embeds sent by the Python bot. For formatting, use Discord's watered down Markdown ~ keep in mind that e.g. the `#` symbol does not create a heading.
 

events/validation.py

@@ -9,7 +9,6 @@
 We check that each event directory satisfies the following:
 * Contains 'meta.md', `banners/` and 'server_icons/' with at least 1 file inside each
 * The 'meta.md' file either registers the event as fallback, or specifies the start and end dates
-* The end date must either be the same as the start date, or chronologically subsequent
 * The 'meta.md' file contains an event description between 1 and 2048 characters in length
 
 If all events are set up correctly, we also validate that: