Formatting not working properly

[S184019]

I've a simple table with a date field called "ServDate" formatted as a date *3/14/2001 with values ranging from 9/4/2018 to 3/29/2019.   The table has ~134K rows. Creating a new column like this

MMM = MONTH(a[ServDate]) 

I get: 

ServDate                      MMM
10/2/2018                    10
10/2/2018                    10
10/18/2018                  10
... so this works. 

But IF, we add this piece, MMM = FORMAT(MONTH(a[ServDate]),"MMM"),  we get 

ServDate                      MMM
10/2/2018                    Jan
10/2/2018                    Jan
10/18/2018                  Jan

The month here is October, not January. Please let me know if you want the pbix. 

[v-qiuyu-msft · Accepted solution]

Hi @S184019, 

Please modify the DAX like below: 

MMM-YY = CONCATENATE(FORMAT(Dates[Date],"MMM"),CONCATENATE("-",RIGHT(YEAR(Dates[Date]),2)))

Best Regards,
Qiuyun Yu 

[S184019]

Even more simply, start from a blank PBIX.  create a new table.   Type this which will produce a 2 year date range of 731 rows: 

Dates = CALENDAR(date(year(now())-2,month(now()),Day(now())),now())

Then add a column to the table like this: 

MMM-YY = CONCATENATE(FORMAT(MONTH(Dates[Date]),"MMM"),CONCATENATE("-",RIGHT(YEAR(Dates[Date]),2)))

One would expect to see values for the 3 letter month and 2 digit year, but instead, only Jan and Dec show up with their associated year.  @bi-support @v-yulgu-msft