Question

A clock is reading 10:27:54.0 (hr:min:sec) when it is discovered to be 4 seconds fast. Explain why it is undesirable to set it back to the right time at that point and show (numerically) how it should be adjusted so as to be correct after 8 seconds have elapsed?

Answer 1

Answer:

(a)Applications Time Stamp Events

(b)S=0.5(W-$T_{skew}$)+$T_{skew}$, where $T_{skew}$≤W≤$T_{skew}$+8.

Explanation:

Some applications assume that clocks always advance, so they could timestamp events under this assumption.

In our case we have the wrong timed clock, say W and the hardware clock H which is supposed to advance at a perfect rate.

We proceed to construct a software clock such that after 8 seconds we can replace the wrong timed clock with the software clock in good conditions.

Let us denote the software clock with S.

Then, S=c(W-$T_{skew}$)+$T_{skew}$ where:

$T_{skew}$=The current Time(10:27:54) and;

c is to be found.

We already know that S=$T_{skew}$+4 when W= $T_{skew}$+8,

So:

S=c(W-$T_{skew}$)+$T_{skew}$

$T_{skew}$+4=c($T_{skew}$+8-$T_{skew}$)+$T_{skew}$

4=8c

c=0.5

We obtain the formula

S=0.5(W-$T_{skew}$)+$T_{skew}$, where $T_{skew}$≤W≤$T_{skew}$+8.