It affects time-based events, just like the Berry Glitch, except it isn't fixable. Effects:
Eevee Happyvolution locked into one or the other
Berry growth stops
Daily freebie Berries
Weekly Frustration/Return TM giveaway
Random TV shows
Secret Base Battles
Shoal Cave is locked at either High or Low Tide meaning you cannot make Shell Bells and if it is locked in high, you cannot access the lowest floor to get Snorunt or the NeverMeltIce- RaikouTCG
In addition, Mirage Island and the Feebas spots are fixed into their current state and positions.
This means that you can still find Feebas, but the tiles you can find it in do not randomly change with the clock. They can still change when you change the Dewford Trendy Phrase or mix records.