Question: I have a requirement to add 10 days to current date and assign it to a variable. But I am getting error:

```
date: illegal option -- d

```

This is what I tried:

```
$> NEW_expration_DATE=$(date -d "+10 days")

```

Result:

```
date: illegal option -- d
Usage: date [-u] [+Field Descriptors]

```

Answer: 
Try this: 
NEW\_expration\_DATE=$(gdate -d "+10 days")
You can check the system with "unmane -a" and do a fine search, for example in AIX can use to get yesterday:

```
YESTERDAY=`TZ=aaa24 date +%Y%m%d`

```