Before you flame him too much just because it mentions 4.1+ doesn't mean it's a 4.1 help file, see below from R6:
Manually Setting the System Time
For IP Office systems without access to a time server, a number of methods to manually set the system time exist. These are available in the IP Office 4.1+. The following method is only supported on these phones: 2410, 2420, 4412, 4424, 4612, 4624, 4610, 4620, 4621, 5410, 5420, 5610, 5620, 5621, 6412, 6424. It is supported on any analog, T3, T3 IP or wireless (IP DECT, 3600, 3700 Series) phones.
· Note: If the IP Office system that is still configured for automatic time updates (on by default), any manually set time and date will be overridden on the next automatic update. The use of automatic updates can be disabled by setting the System | System | Time Server IP Address to 0.0.0.1.
Still no mention of 16XX
ACSS Small and Medium Enterprise (SME) Communications
"What the Crocodile Hat....was that?