+1 on Grant's solution using Lag(1) .. Lag(2), Lag(3) IF YOU DON"T HAVE GAPS IN YOUR DATA.

Only thing I strongly dislike about this approach is that you have to create 3 functions (not efficient) AND it must be true that there are no gaps in data.

Computationally, @GrantSmith i would say this is probably the only good use case for MySQL b/c it allows you to calculate LAG without the assumption of contigusous data (cc. @MarkSnodgrass

NOTE THIS IS ALL UNTESTED CODE there are probably missing commas, and when you set variables (as opposed to display you must use := and variable names are case sensitive.

if you write

SELECT 
t.*
, r.*
FROM 
table t 
, (SELECT @person := '' , @date := null FROM ) r
ORDER BY t.Date

You are CROSS APPLYing a generated table with one row (r) to every row of table t where table r contains variables person and date which are insantiated as blank and null respectively

from there if you write

SELECT 
@date as prevDate,  
t.*,
@date := t.date as _setDateVariable
 
FROM 
table t 
, (SELECT @person := '' , @date := null FROM ) r
 
ORDER BY t.Date

when MySQL reads this function it will process each column of my SELECT statement in order (top to bottom). so when if i was on row 3 of my table...

prevDate is the value of assigned to @date (which happens to be the value of t.date from row 2 -- i'll explain in a second), then it reads all the values for that row of table t, then it assigns @date the value of t.date for the current row (row 3)

when i SELECT row 4...

prevDate is the value of @date (row 3) , t.* is all the contents of row 4, then i assign ( using := ) the value of t.date (row 4) to @date.

and so on.

implement partitioning and test for previous day

SELECT 
-- execute tests. testing @person implements my Partition clause
-- testing @lag1Date ensures the no gaps rule (this is the key part that Magic doesn't give you)
 
case when t.person = @person and @lag1Date = date_add(t.date, interval -1 day) then @lag1Value end as prevDayValue,
t.*,
 
-- paritioning assumes an ORDER BY clause
-- OR reset my variables to null
@lag1Value := case when t.person = @person then t.value else null end as _setLag1Value,
@lag1Date := case when t.person = @person then t.date else null end as _setLag1Date,
   
@person := t.person as _setPersionVariable
 
FROM 
table t 
, (SELECT @person := '' , @date := null , @lag1Value:=null, @lag1Date:=null, FROM ) r
 
ORDER BY t.person, t.Date

Implement Cascading testing

SELECT 
-- execute tests. testing @person implements my Partition clause
-- testing @lag1Date ensures the no gaps rule (this is the key part that Magic doesn't give you)
 
case when t.person = @person and @lag1Date = date_add(t.date, interval -1 day) then @lag1Value end as prevDayValue,
case when t.person = @person and @lag2Date = date_add(t.date, interval -2 day) then @lag2Value end as prevDayValue,
 
t.*,
 
-- cascade the values of lag1 to lag2 or reset to null
@lag2Value := case when t.person = @person then @lag1Value else null end as _setLag2Value,
@lag2Date := case when t.person = @person then @lag2Value else null end as _setLag2Date,
 
@lag1Value := case when t.person = @person then t.value else null end as _setLag1Value,
@lag1Date := case when t.person = @person then t.date else null end as _setLag1Date,
   
@person := t.person as _setPersionVariable
 
FROM 
table t 
, (SELECT @person := '' , @date := null , @lag1Value:=null, @lag1Date:=null, @lag2Value := null lag2Date:=null FROM ) r
 
ORDER BY t.person, t.Date