windows批处理循环递减日期问题

[kernelkoder]

set deldata=%date:~0,4%%date:~5,2%%date:~8,2%

for /L %%i in (0,1,30) do (
   set /a currdata=deldata -%%i
   echo  %currdata%,%%i
)

我的目的是先去当前日期，然后生成字符串，比如
20170817
20170816
20170815
...
但是以上代码无法达到要求，求救！

[auq404]

set deldata=%date:~0,4%%date:~5,2%%date:~8,2%

setlocal ENABLEDELAYEDEXPANSION
 
for /L %%i in (0,1,30) do (
   set /a currdata=deldata -%%i
   echo  !currdata!,%%i
)