Azure YAML based pipeline can not get date and Rev:.r

I am using the new approach of Azure pipeline (hosted YAML file), but in this approach am not able to get date and other embedded variable. I have a variable like below:

variables: 
- name: BuildVersionNumber
  value: $(Date)_$(BuildDefinitionName)_$(TargetReleaseBuildNumber).$(YearChangeIndicator)$(Date:MMdd)$(Rev:.r)

but I get this as a result

$(Date)_$(BuildDefinitionName)_21.570.1$(Date:MMdd)$(Rev:.r)