Calculate the number of days between two given dates. The dates are provided in a specific format, and you need to compute the difference in days.

Design a data structure that acts as a Least Recently Used (LRU) cache. Implement methods to get and put key-value pairs, evicting the least recently used entry when the cache is full.

Implement a circular queue data structure with a fixed size. You'll need to handle enqueueing, dequeueing, and checking if the queue is full or empty efficiently.