Job 8:9

For we are but of yesterday -That is, we are of short life. We have had but few opportunities of observation compared with those who have gone before us. There can be no doubt that Bildad here refers to the longevity of the antecedent ages compared with the age of man at the time when he lived; and the passage, therefore, is of importance in order to fix the date of the poem. It shows that human life had been reduced in the time of Job within comparatively moderate limits, and that an important change had taken place in its duration. This reduction began not long after the flood, and was probably continued gradually until it reached the present limit of seventy years.