Set the date on Linux without NTP

I've recently had a situation where I need a perfect timesync on a server I was logged into, but it had very restricted outbound access. Specifically, it couldn't use NTP to sync time.

This awesome hack gets the date from a webserver (e.g. google) and sets the system time based on that.

date -s "$(curl -s --head http://google.com | grep ^Date: | sed 's/Date: //g')"

Naturally, I don't recommend this as a primary method for fixing time drift, but in a pinch it's great!

Explaining how it works

Lets break it up into it's component pieces:

• date -s sets your local time on Linux.
• curl -s --head http://google.com gets the HTTP headers from Google.com
• grep ^Date: find the line in the headers with Date in it
• sed 's/Date: //g removes the "Date: " part, leaving only the actual date

So what you are really doing is getting the Date from Google.com, altering the text a bit to just have the real date left, and then setting your local time based on that.