Calculation to find previous date value for every date present in the dataset

Hi,

1. Check the Data Type in Power Query . It should be Date Time.

2. Check whether any values are getting summarised by default in the pane. Make all as Don't Summarize.
3.Change Format of all your Date/Time column to the same one. Choose a format which has DD/MM/YYYY hh:mm:ss AM/PM since your data involves all of these

Use these Measures:

Previous Patient No2 =
VAR a =
    MAX ( 'Table6'[Date] )
VAR b =
    CALCULATE (
        MAX ( Table6[Patient No] ),
        FILTER (
            ALL (
                Table6[Patient No],
                Table6[Date],
                Table6[Values]
            ),
            Table6[Date] < a
                && Table6[Patient No]
                    = MAX ( Table6[Patient No] )
        )
    )
RETURN
    b



Previous Date2 =
VAR a =
MAX ( 'Table6'[Date] )
VAR b =
CALCULATE (
MAX ( Table6[Date] ),
FILTER (
ALL (
Table6[Patient No],
Table6[Date],
Table6[Values]
),
Table6[Date] < a
&& Table6[Patient No]
= MAX ( Table6[Patient No] )
)
)
RETURN
b

Previous Value2 =
VAR _previousDate = [Previous Date2]
VAR _patientno = [Previous Patient No2]
RETURN
    CALCULATE (
        MAX ( Table6[Values] ),
        FILTER (
            ALL ( Table6 ),
            Table6[Date] = _previousDate
                && Table6[Patient No] = _patientno
        )
    )

It is working fine for me with Data Type Date Time.

Regards,

Harsh Nathani

Did I answer your question? Mark my post as a solution! Appreciate with a Kudos!!