Time Intelligence based on a specific date as reference

[VickyDev18]

Suppose I have a Scenarios table and a disconnected Period Table  as shown below.

Scenarios
scenario_id	scenario_code	scenario_type	fiscal_year	forecast_start_date
1	2021 JAN	Forecast	2021	2/1/2020
2	2021 FEB	Forecast	2021	3/1/2021
3	2021 MAR	Forecast	2021	4/1/2022
3	2021 APR	Forecast	2021	5/1/2023
4	2021 MAY	Forecast	2021	6/1/2024

Period
period_id	period_code
1	MTD
2	QTD
3	YTD
4	FY

I would like to create 2 measures start_of_period and end_of period that produce the output below if say 2021 MAY was selected. 

Output
scenario_id	scenario_code	scenario_type	fiscal_year	forecast_start_date	period_code	calendar_month	start_of_period	end_of_period
1	2021 MAY	Forecast	2021	6/1/2021	MTD	May-21	5/1/2021	5/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	QTD	Apr-21	4/1/2021	4/30/2021
1	2021 MAY	Forecast	2021	6/1/2021	QTD	May-21	5/1/2021	5/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	YTD	Jan-21	1/1/2021	1/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	YTD	Feb-21	2/1/2021	2/2/2021
1	2021 MAY	Forecast	2021	6/1/2021	YTD	Mar-21	3/1/2021	3/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	YTD	Apr-21	4/1/2021	4/30/2021
1	2021 MAY	Forecast	2021	6/1/2021	YTD	May-21	5/1/2021	5/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Jan-21	1/1/2021	1/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Feb-21	2/1/2021	2/28/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Mar-21	3/1/2021	3/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Apr-21	4/1/2021	4/30/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	May-21	5/1/2021	5/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Jun-21	6/1/2021	6/30/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Jul-21	7/1/2021	7/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Aug-21	8/1/2021	8/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Sep-21	9/1/2021	9/30/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Oct-21	10/1/2021	10/31/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Nov-21	11/1/2021	11/30/2021
1	2021 MAY	Forecast	2021	6/1/2021	FY	Dec-21	12/1/2021	12/31/2021

I tried something like this but it ends up producing a start and end date for all periods/months even when MTD is selected. Ideally, when I select MTD and 2021 MAY, it should only return values for the month of May'21 i.e. result should be 1 row as shown above.
When QTD is selected it should return 2 rows as shown above and not 12 rows. 

start_of_period =
VAR __ReferenceDate = SELECTEDVALUE(Scenarios[forecast_start_date])

VAR __Dates = FILTER(VALUES(Calendar[Date]), Calendar[Date] <= __ReferenceDate)

RETURN
SWITCH (
    SELECTEDVALUE(Period[period_code]),
    "MTD", STARTOFMONTH(__Dates), -- First day of the month    
    "QTD", STARTOFQUARTER(__Dates), -- First day of the quarter    
    "YTD", STARTOFYEAR(__Dates), -- First day of the year    
    "FY", STARTOFYEAR(__Dates) -- First day of the year
)

end_of_period = 
VAR __ReferenceDate = SELECTEDVALUE(Scenarios[forecast_start_date])

VAR __Dates = FILTER(VALUES(Calendar[Date]), Calendar[Date] <= __ReferenceDate)

RETURN
SWITCH (
    SELECTEDVALUE(Period[period_code]),
    "MTD", ENDOFMONTH(__Dates), -- Last day of the month    
    "QTD", ENDOFMONTH(__Dates), -- Last day of the month    
    "YTD", ENDOFMONTH(__Dates), -- Last day of the month    
    "FY", ENDOFYEAR(__Dates) -- Last day of the year
)

[Bibiano_Geraldo]

HI, Make sure your Calendar table is connected appropriately and try this:

start_of_period = 
VAR __ReferenceDate = SELECTEDVALUE(Scenarios[forecast_start_date])
VAR __SelectedPeriod = SELECTEDVALUE(Period[period_code])
VAR __StartOfMonth = STARTOFMONTH(__ReferenceDate)
VAR __StartOfQuarter = STARTOFQUARTER(__ReferenceDate)
VAR __StartOfYear = STARTOFYEAR(__ReferenceDate)

RETURN 
SWITCH(
    __SelectedPeriod,
    "MTD", __StartOfMonth,  -- Start of the month for MTD
    "QTD", __StartOfQuarter,  -- Start of the quarter for QTD
    "YTD", __StartOfYear,  -- Start of the year for YTD
    "FY", __StartOfYear  -- Start of the fiscal year for FY
)

end_of_period = 
VAR __ReferenceDate = SELECTEDVALUE(Scenarios[forecast_start_date])
VAR __SelectedPeriod = SELECTEDVALUE(Period[period_code])
VAR __EndOfMonth = ENDOFMONTH(__ReferenceDate)
VAR __EndOfQuarter = ENDOFQUARTER(__ReferenceDate)
VAR __EndOfYear = ENDOFYEAR(__ReferenceDate)

RETURN 
SWITCH(
    __SelectedPeriod,
    "MTD", __EndOfMonth,  -- End of the month for MTD
    "QTD", __EndOfQuarter,  -- End of the quarter for QTD
    "YTD", __EndOfMonth,  -- End of the month (could change for YTD but typically aligns with current month)
    "FY", __EndOfYear  -- End of the fiscal year for FY
)

[VickyDev18]

This gives an error stating that STARTOFMONTH expects a column. I tried adding a new variable  __Dates and passed that instead of  __ReferenceDate but that is producing a blank. 

VAR __Dates = FILTER(VALUES(Calendar[Date]), Calendar[Date] = __ReferenceDate)

Here's a link to a -> sample PBIX file