Report expression convert prompt date to string in report studio

[tarunkrdas2013]

Hi,

can someone help in converting below  prompt date to string in Report studio..Its a DMR report

union(
       union(
       union(
       member(aggregate(currentMeasure within set (periodsToDate ([DMR].[Fiscal Calendar].[Fiscal Calendar].[Fiscal Date],[DMR].[Fiscal Calendar].[Fiscal Calendar].[Fiscal Date]->[all].[@MEMBER].#sb(timestampmask(prompt('p_Date','Date', _add_days ($current_timestamp,-1),'','','T00:00:00Z'),'yyyymmdd'))#))),'DAILY','DAILY',[DMR].[Fiscal Calendar].[Fiscal Calendar])
       ,
       member(aggregate(currentMeasure within set (periodsToDate ([DMR].[Fiscal Calendar].[Fiscal Calendar].[Fiscal Week],[DMR].[Fiscal Calendar].[Fiscal Calendar].[Fiscal Date]->[all].[@MEMBER].#sb(timestampmask(prompt('p_Date','Date', _add_days ($current_timestamp,-1),'','','T00:00:00Z'),'yyyymmdd'))#))),'WTD','WTD',[DMR].[Fiscal Calendar].[Fiscal Calendar])
       )
       ,
       member(aggregate(currentMeasure within set (periodsToDate ([DMR].[Fiscal Calendar].[Fiscal Calendar].[Fiscal Period],[DMR].[Fiscal Calendar].[Fiscal Calendar].[Fiscal Date]->[all].[@MEMBER].#sb(timestampmask(prompt('p_Date','Date', _add_days ($current_timestamp,-1),'','','T00:00:00Z'),'yyyymmdd'))#))),'PTD','PTD',[DMR].[Fiscal Calendar].[Fiscal Calendar])
       )
       ,
       member(aggregate(currentMeasure within set (periodsToDate ([DMR].[Fiscal Calendar].[Fiscal Calendar].[Fiscal Year],[DMR].[Fiscal Calendar].[Fiscal Calendar].[Fiscal Date]->[all].[@MEMBER].#sb(timestampmask(prompt('p_Date','Date', _add_days ($current_timestamp,-1),'','','T00:00:00Z'),'yyyymmdd'))#))),'YTD','YTD',[DMR].[Fiscal Calendar].[Fiscal Calendar])
       )