why i can change date using telnet

I want to change the date from remote side,but I found I can’t change the data by telnet,even if i log on of root

The problem is not telnet. What are you doing to change the date? You have to change the system clock with “date” and then set the CMOS clock with rtc. Does that help?

just as you said,I change the system clock with “date”,but it 's only valid on local command,when I use telnet to log on and try to use date,it fails.

by the way,when I use date there’s no failure message and show the right time on the next line,but if you use date to check if it has been changed,you will find no.

rtc, rtc, rtc, rtc:

use rtc

another question:I can change the date,but when the system reboots it restores to the date changed before,in other word how can i change the bios date?

PLEASE read the documentation on date and rtc.