Switch between weekly and monthly Views

Hi Diego-mx,

Solution 2. 
I create a secondary grouping calendar table with "long" format (as opposed to wide format), with columns "b_date" and "period" that looks like this: 

b_date      period 
7/1/2018   "month"
8/1/2018   "month"
9/1/2018   "month" 
... 
7/1/2018   "week"
7/8/2018   "week"
7/15/2018  "week" 
....

and this becomes easier to link but then I don't know how to create this table as a union of two tables with DAX syntax. 

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You can create a calculated table as below:

CalendarTable2 =
UNION (
    SELECTCOLUMNS (
        CalendarTable1,
        "b_date", CalendarTable1[week_date],
        "period", "Week"
    ),
    SELECTCOLUMNS (
        CalendarTable1,
        "b_date", CalendarTable1[month_date],
        "period", "Month"
    )
)

Best regards,

Yuliana Gu