为什么常用crontab，却忽略windows任务计划呢？

比如这是个删除60天以前的日志
-----------------------hollyDeleteLog.bat-------------------------------
@echo off
rem 计算指定天数之前的日期 edit by raojl 2010-05-17
set DaysAgo=60
rem 假设系统日期的格式为yyyy-mm-dd
callateToDays %date:~0,4% %date:~5,2% %date:~8,2% PassDays
set /a PassDays-=%DaysAgo%
callaysToDate %PassDays% DstYear DstMonth DstDay
d:
cd \CommH2Proxy\log
del Unicom3g-%date:~0,4%-%DstMonth%*.log
echo %date%:Unicom3g-%date:~0,4%-%DstMonth%*.log 被成功删除!>>batexe.log
goto :eof

:DateToDays %yy% %mm% %dd% days
setlocal ENABLEEXTENSIONS
set yy=%1&set mm=%2&set dd=%3
if 1%yy% LSS 200 if 1%yy% LSS 170 (set yy=20%yy%) else (set yy=19%yy%)
set /a dd=100%dd%%%100,mm=100%mm%%%100
set /a z=14-mm,z/=12,y=yy+4800-z,m=mm+12*z-3,j=153*m+2
set /a j=j/5+dd+y*365+y/4-y/100+y/400-2472633
endlocal&set %4=%j%&goto :EOF

:DaysToDate %days% yy mm dd
setlocal ENABLEEXTENSIONS
set /a a=%1+2472632,b=4*a+3,b/=146097,c=-b*146097,c/=4,c+=a
set /a d=4*c+3,d/=1461,e=-1461*d,e/=4,e+=c,m=5*e+2,m/=153,dd=153*m+2,dd/=5
set /a dd=-dd+e+1,mm=-m/10,mm*=12,mm+=m+3,yy=b*100+d-4800+m/10
(if %mm% LSS 10 set mm=%mm%)&(if %dd% LSS 10 set dd=0%dd%)
endlocal&set %2=%yy%&set %3=%mm%&set %4=%dd%&goto :EOF