ADJTIME(2) Linux Programmer's Manual ADJTIME(2)
adjtime - smoothly tune kernel clock
int adjtime(const struct timeval *delta, struct timeval *olddelta);
This function speeds up or slows down the system clock in order to make
a gradual adjustment. This ensures that the calendar time reported by
the system clock is always monotonically increasing, which might not
happen if you simply set the clock.
The delta argument specifies a relative adjustment to be made to the
clock time. If negative, the system clock is slowed down fora while
until it has lost this much elapsed time. If positive, the system
clock is speeded up for a while.
If the olddelta argument is not a null pointer, the adjtime function
returns information about any previous time adjustment that has not yet
This function is typically used to synchronize the clocks of computers
in a local network. You must be a privileged user to use it.
The adjtime function returns 0 on success and -1 on failure and sets
the external variable errno accordingly.
EPERM The calling process does not have enough privileges to access
With a Linux kernel, you can use the adjtimex(2) function to perma-
nently change the system clock speed.
This function is derived from 4.3 BSD and SVr4.
Linux 2.0 2002-02-16 ADJTIME(2)