In the block sensing, how to use “username” and “days since 2000”
please explain me

“username” reports the username of the user using the project. If the user is not logged in, it will report “0”

days since 2000 reports the number of days that have passed since the year 2000 in a long decimal. For example, it's been 4932 days since then as of today.

Ideas:

1.Greet the user at the start of a game
2.Make a calendar
3.Make a special message for specific users
4.Make a “Is it (New Years)?” Project

Hope these give you some ideas for what to use these blocks with.