If you would like to display the week numbers for the current year in Windows 10’s Calendar app, you will need to enable a small setting. Here are the instructions on how to show week numbers (based on a specific week numbering system) in the Calendar app.
Display Week Numbers in Calendar View
Open the Calendar app, click on the Cog icon and go to Settings > Calendar Settings:
Click on the drop down menu below Week numbers and select the desired week numbering system. You can, for example, choose to start your first week on the First Day of Year, after the First Full Week, or after the First Four-Day Week:
Moving forward, the Calendar app will add new column for week numbers: