For most weights and measures there are both Imperial and Metric equivalents, pounds and kilos, litres and gallons, but I can't think of an equivalent for time itself.
Seconds may get divided into milliseconds and nanoseconds as orders of ten, but above that we use minutes and hours in imperial multiples of sixty.
So how would you go about metricising time?
What level would you start at - the length of time the earth rotates on it's axis, or the length of time the earth rotates around the sun? Is there an arbitrary alternative you could use?
If we did, should we keep the same distinct names or should we find different ones? Would a second be changed to have a new length or should we stop using seconds and rename units of time.
How many things would have to change if we did this. and what kind of confusion would this cause?