rrdtool问题

xyx219

执行命令：
rrdtool create eth0.rrd \
--start $(date –d ‘1 days ago’ +%s) \
--step 300 \
DS:eth0_in:COUNTER:600:0:12500000 \
DS:eth0_out:COUNER:600:0:12500000 \
RRA:AVERAGE:0.5:1:600 \
RRA:AVERAGE:0.5:4:600 \
RRA:AVERAGE:0.5:24:600 \
RRA:AVERAGE:0.5:288:730

错误信息：
date: extra operand `‘1'
Try `date --help' for more information.
ERROR: start time: There should be number after '-'


求助，这条语句哪里有问题。