smartctl to find how old is the hard drive

I just got a new server from a server provider and he placed in some old 1.5TB HDD. They do support smartctl.

Is there a way I can findout how old these drives are?

If you want to know the HDD's manufacture date (e.g. for warranty issues) the only universal way to get that is to open the case and have a look at the HDD label.

Another possible way is to use hdparm -i /dev/sdx or smartctl -a /dev/sdx to get the model and serial number and check with the manufacturer's warranty web page. Some manufacturers will provide a manufacture date for each serial number.

smartctl -a /dev/sdx will occasionally have a Power_On_Hours or other similar attribute which can be an indicator of how long a drive has been in use. Other attributes may also serve this way.

EDIT:

For example Seagate provides the warranty expiration date, which can be used to estimate the manufacture date if you know the length of the warranty period. The length of the warranty period usually depends on the model and you should be able to find it by searching the web.