Doesn't work in Sketch

[optimix-designer]

Unfortunately I couldn’t get it working 😢 Each time I get a text like “Dates (mm-dd-y)” instead of actually get a date. Tried in different versions of Sketch, nothing helped.
Here’s a short screencast: http://quick.as/56V3Hox3Q
Maybe you can explain me what I’m doing wrong? Any help is appreciated 😊 Thank you in advance!