A two-week-long event Lapis Lakeside Opening lasts from Monday, January 29th, 2024 until Monday, February 12th, 2024.

Event: Lapis Lakeside Opening

An opportunity to research Lapis Lakeside Pokémon—on Greengrass Isle! The two-week-long event Lapis Lakeside Opening lasts from 4:00 a.m. on Monday, January 29 until 3:59 a.m. on Monday, February 12. Dratini, Ralts, and Stufful, who live at Lapis Lakeside, will also appear on Greengrass Isle during the Lapis Lakeside Opening event only!

Note: Regarding Dratini, Ralts, and Stufful
・ After the event, they will no longer appear during sleep research on Greengrass Isle (except when using that Pokémon’s incense).

Through limited-time missions during the event, you can get great rewards such as Dratini Incense, Ralts Incense, and Stufful Incense. And this time, we have two sets of missions: Week 1 Missions and Week 2 Missions!

Notes: The limited-time missions are available in all areas.

Regarding Dratini Incense, Ralts Incense, and Stufful Incense

・ Once a week has passed after the event, you’ll no longer be able to use them on Greengrass Isle.
・ If you haven’t yet unlocked Lapis Lakeside, we recommend that you use these Incenses on Greengrass Isle by 1:00 p.m. on Monday, February 19.

Week 1 Missions: Monday, January 29, at 4:00 a.m. to Monday, February 12, at 3:59 a.m.
Week 2 Missions: Monday, February 5, at 4:00 a.m. to Monday, February 12, at 3:59 a.m.

We hope you’re looking forward to the event!

How to Progress in the Event

Participating in the event is easy! Simply press the “Sleep” button on Greengrass Isle before going to sleep during the event period to track your sleep.
Note: If you track your sleep on areas other than Greengrass Isle or Lapis Lakeside during the event, you won’t meet Dratini, Ralts, or Stufful in your sleep research.

Pokémon that are easier to encounter during the event

During the event period, the following Pokémon are more likely to appear!
Slightly Greater Appearance Rate
Dratini, Ralts, and Stufful

To Researchers Who Have Unlocked Lapis Lakeside

If you want to encounter Dratini, Ralts, or Stufful, we recommend that you research at Lapis Lakeside. You are more likely to encounter these Pokémon there than on Greengrass Isle during the event period.

Notes about the Lapis Lakeside Opening Event

• [Important] Each day of the Lapis Lakeside Opening event rolls over at 4:00 a.m.
• [Important] If you track your sleep on areas other than Greengrass Isle or Lapis Lakeside during the event, you won’t meet Dratini, Ralts, or Stufful in your sleep research.
• [Important] After the event, Dratini, Ralts, and Stufful will no longer appear during sleep research on Greengrass Isle (except when using that Pokémon’s incense).
• [Important] Once a week has passed after the event, you’ll no longer be able to use Dratini Incense, Ralts Incense, or Stufful Incense on Greengrass Isle.

Source: https://www.pokemonsleep.net/en/news/4557/