It will now be possible to create custom calendars, eg: fiscal year calendar instead of the normal calendar.

How does it work?

You can setup a Calendar within the Calendar options of your date table. You give your custom Calendar a name and match the several time categories to you columns.

Eg: ‘Calendar’ and matching Year, Month and Date Fields AND ‘Fiscal Calendar’ matching FiscalYear, FiscalMonth, Date fields.

That way you will have 2 calendars set up based on your Date columns and data. And DAX will be able to use the calendar in its calculations.

Eg:
Sales MTD = TOTALMTD ( [Total Sales], ‘Calendar’ )
OR
Sales Same Period Last Fiscal Year = CALCULATE ( [Total Sales], SAMEPERIODLASTYEAR( ‘Fiscal Calendar’ ) )

2. Performance analyzer in web

While in edit mode, you can now use the performance analyzer to check load times. (This was previously only possible in PBI Desktop).

Modeling

1.  A bunch of in PREVIEW features have been made Generally Available:

• Edit of Semantic Models in Service
• Live Edit of Direct Lake Semantic Models in PBI Desktop
• TMDL View
• Fabric Notebooks, “Best Practice Analyzer” and “Memory Analyzer”

2. PBIX models with altered XMLA in PBI Desktop

With the GA over TMDL view it is now possible to download and open/edit them within PBI Desktop.

3. DAX User Defined Functions (PREVIEW)

UDF are now supported to be used within DAX. These will act similar to functions or methods you would see in programming. So basically, items you can re-use in your DAX expression once they’ve been defined. You were able to re-use DAX logic already through calculation groups, but now you’ll be able to do this with any DAX logic AND you’ll be able to have them set up with parameters!

A fun example for icons:
https://www.reddit.com/r/PowerBI/comments/1nmcbqp/udfs_introduce_a_new_way_to_manage_your_icons/

A detailed walkthrough by SQLBI:
https://www.youtube.com/watch?v=60jUmTxpxbw

Another video with some interesting examples:
https://www.youtube.com/watch?v=kynJmgls6A4

4. Refresh data or schema in PBI Desktop

When trying to refresh in PBI Desktop you now get the option to refresh the schema and data (what was the case in the past). But also the options to refresh one of the two individually (only schema or only data).

In the past it would be first it performs a schema refresh and then performs the data refresh. With the 2 extra options you can:

• Sync schema only, your model will reflect the new data structure like column type change or new columns without affecting the data.
• Sync data only, your data will be refreshed and you model/schema remains the same. Even if a change was done in your data source.

Read more in the Power BI Blog Post.