Salesforce announced Summer ’21 release details.

Below are the Key dates for the Salesforce Summer ’21 release.

April 15, 2021 : Pre-Release orgs available for sneak preview of the new features. 
Pre-Release Org Sign up ->  Click here

April 20, 2021:  Salesforce Help is the new home for the release notes, with an improved user experience, an updated UI, scoped search, and filters when viewed on a desktop.

Release Notes -> Click here

      May 6, 2021: Sandbox CUTOFF date -> Salesforce Help gives you the option to participate in the sandbox preview.
      For your sandbox to get the Summer ‘21 preview, take action before 6 pm Pacific Time on May 6, 2021.

      Click here to read sandbox preview instructions

May 7-8, 2021:
Sandbox Preview Starts -> Click here
Release Site -> Click here
Release Badge on Trailhead  -> Click here

      May 11, 2021:
      Release Overview Deck & Feature Matrix -> Click here

May 21 -28, 2021:
Release Readiness Live -> Click here

May 14, 2021, June 4, 2021 & June 11, 2021:
Summer ’21 is LIVE -> Click here

       Now once a year!
       All certifications now require the completion of only one maintenance module per year. 

       Find out which maintenance module is required by each certification on Trailhead -> Click here