Date Simulation Modulator
Sold by Dawn Radue. This toy will place a machine in front of you that you can interact with to change the sky's appearance/weather effect.
The 
Date Simulation Modulator is a toy that lets you change the sky's appearance and weather effects in your current zone.
Guide awaiting review
Purchase from vendor
Find Dawn Radue at 64.8, 71.4 in Stormwind City and purchase the Date Simulation Modulator. The toy is bind on use, so you can also buy it from the Auction House if you prefer.
Use the toy
Activate the Date Simulation Modulator to place a machine in front of you. Interact with it to cycle through sky effects: Peaceful Day (blue sky), Romantic Sunset (pink/orange sky), Fireflies at Midnight (night with fireflies), Stuck in a Rainstorm (rain and clouds), or Kick the machine to return to normal.
