Confusion in table connection for showing Trend

[Composed_MS]

Hello,

I need to show the trend of previous 12 months data from the MonthYear selected in the slicer.

So, for this I have created duplicate of Calendar table (named Calendar2) and then created the connection as below with my fact table and main Calendar table.
Notice that the connection between Calendar table and Calendar2 table is inactive.

I am using below measure to show trend->

Trend =

var previous_dates=DATESINPERIOD(Calendar2[Date],MAX(Calendar[Date]),-12,MONTH)

return

 CALCULATE([Measure],

    REMOVEFILTERS('Calendar'),

    KEEPFILTERS(previous_dates),

    USERELATIONSHIP('Calendar'[Date],Calendar2[Date]))

This is showing the correct trend (I am keeping MonthYear from Calendar2 table in X axis), but I am getting confused that why we are not creating a direct active connection between fact table and Calendar2 table as well, here if you see there's no connection between fact table and Calendar2 table.

Why can't we do that? When will I face the issue if I do this?

Can anyone please explain?

[amitchandak]

@Composed_MS , if you want show trend based on selected value, then calendar 2 should not join with any table

//Date1 is independent Date table, Date is joined with Table
new measure =
var _max = maxx(allselected(Date1),Date1[Date])
var _min = eomonth(_max, -12) +1
return
calculate( sum(Table[Value]), filter('Date', 'Date'[Date] >=_min && 'Date'[Date] <=_max))

Need of an Independent Date Table:https://www.youtube.com/watch?v=44fGGmg9fHI

[Composed_MS]

Hello @amitchandak 

I need to select MonthYear from Calendar table date slicer and in trend I am showing Calendar2 dates, so for that I am connecting my Calendar table with Calendar2 table inactively and then using Userrelationship function.
That thing is not creating any issue as it is giving me the correct trend from the "Trend" measure I wrote above.
My confusion is why do we not create the direct relationship of Calendar2 with fact table?