Get Max date below to the context filter

Sorry, my mistake. Please try this one

var min_day_slicer = if (ISFILTERED('calerdar[date]), MIN ('calerdar[date]), MAX ('calerdar[date]))

              return MAXX(CALCULATETABLE(purchase,REMOVEFILTER('calerdar[date]),'purchase[trnx_date] < min_day_slicer),'purchase[trnx_date])

I tried below code and it worked.

calculate(
        max(purchases[trnx_date]),
        datesinperiod('calendar'[date],startofmonth('calendar'[date])-1,-48,MONTH)
)

but letter Hoangechip910 has given a better solution and I adopted the same. Below is his code.

var min_day_slicer = if (ISFILTERED('calendar'[date]), MIN ('calendar'[date]), MAX ('calendar'[date]))
return MAXX(
    CALCULATETABLE
        (
            purchases,
            REMOVEFILTERS('calendar'[date]),
            'purchases'[trnx_date] < min_day_slicer
        ),
        'purchases'[trnx_date]
    )

Thank you everyone for your time and support. ❤️