Formula today -1 month

Hi Anonymous 

Today is 2019/10/18, so this month is from 2019/10/1~2019/10/18, last month is from 2019/9/1~2019/9/18

Create measures

current =
CALCULATE (
    DISTINCTCOUNT ( Sheet1[visitor] ),
    FILTER (
        'date table',
        'date table'[year] = YEAR ( TODAY () )
            && 'date table'[month] = MONTH ( TODAY () )
            && 'date table'[Date] <= TODAY ()
    )
)

today-1_month =
CALCULATE (
    DISTINCTCOUNT ( Sheet1[visitor] ),
    DATEADD (
        FILTER ( DATESMTD ( 'date table'[Date] ), 'date table'[Date] <= TODAY () ),
        -1,
        MONTH
    )
)

Try

= Date.AddMonths(DateTime.Date(DateTime.LocalNow()),-1)