如果 TIMEIN 始终为六个字符(即，上午10点之前的时间前导零)，则可以执行以下操作:

If TIMEIN is always six characters (i.e., there's a leading zero for times before 10 AM), then you can do this:

df$TIMEIN = paste0(substr(df$TIMEIN,1,2),":",substr(df$TIMEIN,3,4),":", substr(df$TIMEIN,5,6))
df$TIMEIN = hms(df$TIMEIN)