Monthly YoY comparison

mcha17 , Create a date from the month

Date =  date(left([Month],4) , right([Month],2) , 1)

Have all required columns in the date table and join it with your date now 

Then you can use TI

Year behind Sales = CALCULATE(SUM(Table[Value]),dateadd('Date'[Date],-1,Year))
Year behind Sales = CALCULATE(SUM(Table[Value]),SAMEPERIODLASTYEAR('Date'[Date]))

MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD('Date'[Date]))


last year MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD(dateadd('Date'[Date],-12,MONTH)))
Previous year Month Sales = CALCULATE(SUM(Sales[Sales Amount]),previousmonth(dateadd('Date'[Date],-11,MONTH)))

Else create a new table with Month(You have call it year month) , Year and month (number 1 - 12) , Assume name is date table

Join it back with your table 

This Month = CALCULATE(sum('Table'[Qty]), FILTER(ALL('Date'),'Date'[Year]=max('Date'[Year]) && Date[Month]=max(Date[Month])))
Last year same Month= CALCULATE(sum('Table'[Qty]), FILTER(ALL('Date'),'Date'[Year]=max('Date'[Year])-1 && Date[Month]=max(Date[Month])))

calendar

Calendar = Addcolumns(calendar(date(2020,01,01), date(2021,12,31) ), "Month no" , month([date])
, "Year", year([date])
, "Month Year", format([date],"mmm-yyyy")
, "Month year sort", year([date])*100 + month([date])
, "Qtr Year", format([date],"yyyy-\QQ")
, "Qtr", quarter([date])
, "Month",FORMAT([Date],"mmmm")
, "Month sort", month([DAte])
, "FY Year", if( Month(_max) <7 , year(_max)-1 ,year(_max))
, "Is Today" ,if([Date]=TODAY(),"Today",[Date]&"")
,"Day of Year" , datediff(date(year([DAte]),1,1), [Date], day)+1
, "Month Type", Switch( True(),
eomonth([Date],0) = eomonth(Today(),-1),"Last Month" ,
eomonth([Date],0)= eomonth(Today(),0),"This Month" ,
Format([Date],"MMM-YYYY") )
,"Year Type" , Switch( True(),
year([Date])= year(Today()),"This Year" ,
year([Date])= year(Today())-1,"Last Year" ,
Format([Date],"YYYY")
)
)

Time Intelligence, Part of learn Power BI https://youtu.be/cN8AO3_vmlY?t=27510
Time Intelligence, DATESMTD, DATESQTD, DATESYTD, Week On Week, Week Till Date, Custom Period on Period,
Custom Period till date: https://youtu.be/aU2aKbnHuWs&t=145s

https://community.powerbi.com/t5/Community-Blog/Creating-Financial-Calendar-Decoding-Date-and-Calendar-1-5-Power/ba-p/1187441
https://medium.com/chandakamit/cheat-sheet-calendar-of-any-standard-month-just-one-variable-apart-5ee47de6a208
https://amitchandak.medium.com/cheat-sheet-power-query-financial-year-calendar-5ceaacb520f1