NTP Servers Used by Windows Mobile 6.5

Windows Mobile 6.5 relied on the Simple Network Time Protocol (SNTP) and cellular network signals to keep device clocks accurate. By default, devices connecting through Wi-Fi or cellular data synchronized with Microsoft's primary time server, time.windows.com, while also allowing manual reconfiguration through the Windows CE registry.

The Default NTP Server

The factory default time synchronization server hardcoded and pre-configured in Windows Mobile 6.5 was:

  • time.windows.com

This is the same global Network Time Protocol (NTP) server used across standard desktop Windows releases. Whenever the device established an active internet connection—via Wi-Fi, a cellular data connection (GPRS, EDGE, 3G), or a tethered ActiveSync/Windows Mobile Device Center pass-through connection—the background time service queried this server using UDP port 123 to adjust the internal real-time clock (RTC).

Cellular Synchronization via NITZ

While time.windows.com handled IP-based network time synchronization, many Windows Mobile 6.5 devices also relied on Network Identity and Time Zone (NITZ). Provided directly by mobile network operators through GSM and CDMA cellular towers, NITZ automatically updated the device's clock and local time zone without requiring an active data session or an NTP request.

In carrier-branded ROMs, NITZ often took precedence over NTP. When cellular service was lost or unavailable, the device defaulted back to local time keeping and standard SNTP synchronization over available data channels.

Registry Configuration and Alternative Servers

Network administrators and advanced users could redirect the operating system to alternate NTP servers by modifying the Windows CE registry. Windows Mobile 6.5 handled time services via the Timesvc module.

The NTP configuration settings were located at:

  • Registry Key: [HKEY_LOCAL_MACHINE\Services\Timesvc]
  • Value Name: Server
  • Type: REG_SZ (String)
  • Default Value: time.windows.com

Common alternatives configured in corporate deployments or regions with latency issues included:

  • time.nist.gov (National Institute of Standards and Technology)
  • pool.ntp.org (The public NTP Pool Project)
  • Local corporate Active Directory domain controllers acting as internal NTP hosts.

Additional registry keys under Timesvc, such as refresh (which defined the sync interval in milliseconds) and recoveryrefresh, controlled how often the device contacted the designated server to correct clock drift.