Hi Marc,
BO Cloud doesn't seem to have a YTD, MTD components like you would with Design Studio. However, I found the following two options really helpful to achieve what you're looking for.
The quick and dirty:
Create a time-series chart. The chart has a prebuilt YTD filter, as well as other nice filters as you can see below.
Image may be NSFW.
Clik here to view.
Otherwise, you can use input control (filters) in the following manner. Still does the job.
Image may be NSFW.
Clik here to view.
Final look:
Image may be NSFW.
Clik here to view.
As you see in the final picture. I am technically showing YTD. The user has to change "May" to "June" when June's data come in.
I hope this help!