If you want to use the date to create a date index column you can use the following DAX:
( YEAR ( MyDates[Date] ) * 10000 )
+ ( MONTH ( MyDates[Date] ) * 100 )
+ DAY ( MyDates[Date] )
So if the date is 31st July 2018 this create an index of 20180731.
You can also do the same in M in the Query Editor window.