NTP

What is NTP?

NTP is a protocol to synchronizing the clocks on host using publicly available NTP servers.

Many Linux Distros provides time servers:

0.debian.pool.ntp.org
1.debian.pool.ntp.org
2.debian.pool.ntp.org

Some big companies too:

time.google.com

Or educational institutions:

time.mit.edu

Or individuals and volunteers:

us.pool.ntp.org
ua.pool.ntp.org

https://developers.google.com/time/: Free, global time service with leap-smeared time.
https://www.ntppool.org/en/: Big virtual cluster of timeservers.

Install ntpdate package:

$ sudo apt-get install ntpdate

and sync date with some NTP server:

# sudo ntpdate 0.debian.pool.ntp.org

See:

http://support.microsoft.com/kb/q216734/: Windows Time Service Tools and Settings.
http://support.microsoft.com/kb/q223184/: How to configure an authoritative time server in Windows 2000.
http://support.microsoft.com/kb/307897/: How to synchronize the time with the Windows Time service in Windows XP.
http://support.microsoft.com/kb/216734/: How to configure an authoritative time server in Windows 2000.