Pocket D is a pocket dimension. It's wherever DJ Zero says it is.
What's funny is that calendar almost lines up to the current year but is off by one day. Ok, not really odd since the calendar does that every once in awhile. You will be able to reuse a 2020 calendar in 2048 , 2076 and 2116. For 2020 you can reuse a calendar from 1992, 1964, 1936, 1908, and 1896.