I go there and I've beaten the game and it's 6:30 and from what I've read that falls under evening in spring for this and it still says "the royal Unova only operates in the evening. Please come back again" anyone got any idea why?
The ship sets sail every day from Castelia City's Cruise Dock. It sets sail in the evening, which starts when day begins visually fading into night and ends when daylight is completely gone. It can be traveled on after obtaining the National Pokédex BW or as soon as the player arrives at Castelia City B2W2. The player can only sail on the ship once per day.
Source
A few things to check with this in mind:
Different seasons have different definitions of "evening". Ensure you're trying at the following times: 17:00–19:59 in Spring, 19:00–20:59 in Summer, 18:00–19:59 in Autumn, or 17:00–18:59 in Winter. You can check which season you're in when you boot up the save file.
Check your DS clock; make sure it's set to the proper time. You say it's 6:30, but the Nintendo DS family uses 24 hour clock. 6:30 PM should be 18:30.
Make sure you have obtained the National Dex.
Ensure this is the first time you have ridden it today (it sounds like you haven't yet, but obligatory mention)
Lastly, if all of the above doesn't help, make sure your game is Authentic. All Gen 5 Pokémon Games use a black-coloured cartridge. If you are using an Emulator or unauthentic copy of the game, unexplained errors can occur with no fix.
I hope this helps!
