Divine Arithmetic

So teach us to number our days, that we may apply our hearts unto wisdom. (Ps. 90.12)

John Calvin on Ps. 90.12:

It indeed seems at first sight absurd to pray that we may know the number of our years. What? since even the strongest scarcely reach the age of fourscore years, is there any difficulty in reckoning up so small a sum? Children learn numbers as soon as they begin to prattle; and we do not need a teacher in arithmetic to enable us to count the length of a hundred upon our fingers. So much the fouler and more shameful is our stupidity in never comprehending the short term of our life. Even he who is most skillful in arithmetic, and who can precisely and accurately understand and investigate millions of millions, is nevertheless unable to count fourscore years in his own life. It is surely a monstrous thing that men can measure all distances without themselves, that they know how many feet the moon is distant from the center of the earth, what space there is between the different planets; and, in short, that they can measure all the dimensions both of heaven and earth; while yet they cannot number threescore and ten years in their own case. It is therefore evident that Moses had good reason to beseech God for ability to perform what requires a wisdom which is very rare among mankind. The last clause of the verse is also worthy of special notice. By it he teaches us that we then truly apply our hearts to wisdom when we comprehend the shortness of human life. What can be a greater proof of madness than to ramble about without proposing to one’s self any end? True believers alone, who know the difference between this transitory state and a blessed eternity, for which they were created, know what ought to be the aim of their life. No man then can regulate his life with a settled mind, but he who, knowing the end of it, that is to say death itself, is led to consider the great purpose of man’s existence in this world, that he may aspire after the prize of the heavenly calling.

Charles Howe, Devout Meditations, pp. 34-35:

XXXIII. Most men are ready enough to reckon up the income of their estates, and compute how it will answer their several expences: but few employ their arithmetic to calculate the value and income of their life and time, or consider how they may be expended to the best advantage. In these the beggar has as large a revenue as the king, though they are justly accounted the more valuable treasure. The gracious God has distributed equal portions of these to all degrees and conditions of men, though not to every particular man the same proportion; and the sum total of this is threescore and ten years, all beyond that being labour and sorrow; and many years also on this side of it. Now we have to consider how much of this is likely to be spent in happiness and enjoyment, and how much will be employed to less pleasing purposes; which may be thus easily computed: twenty years may be deducted for education, which is a time of discipline and restraint, and young people are never easy till they are got over it; and the last ten years of the seventy may be deducted for sickness and infirmities, which very often is the portion of those years: so that these thirty, taken out of life, there remain but forty; out of which a third part, being at least eight hours in the four and twenty, which amounts to be about fourteen years more, must be deducted for sleep, that sister and image of death; and then there remain but twenty-six; and then there remain but twenty-six; out of which, when the requisite allowances are taken for the time we are made uneasy with our own passions, and tormented with other peaople's; for what passes in sickness, pain, loss, and affliction, what we consume in anxiety for things that must inevitably happen, and what in anguish for accidents irrecoverably past; what passes in stupid and insipid amusements, or brown studies, without either trouble or pleasure; when this is summed up, the poor inconsiderable remainder, I doubt, we shall not account much better for; it being generally unprofitably wasted in vice and vanity.

Simon Patrick, Divine Arithmetic; or, The Right Art of Numbering Our Days, in Works, Vol. 7, pp. 505, 514-515, 517-518:

The right numbering of our days is earnestly and diligently to be inquired out. It is plain enough from the prayer of this man of God. For his prayer for learning show that we are highly concerned in the numbering of our days;...

We must reckon our days by our work, and not by our time, by what we do, and not by what we are. Let us account that the longest day which is best spent, and that the oldest life which is most holy....A long life is not the best, but a good life. As we do not commend (saith he) him that hath played a great while on an instrument, or made a long oration, but him that hath played and spoken well...They are the worthiest persons, and have lived longest in the world, who have brought the greatest benefit unto it, and made the great advantage of their time to the service of God and of men. Le our conscience therefore be the ephemeris or diary of our life. Let us not reckon by the almanack, but by the book of God, how much we live. And let us account that he who lives godlily lives long; and that other men live not at all....

We must not account all days alike: or we must not measure our time by the length, but by the weight; not by its greatness, but by its worth. Let us not measure our days (as we do) by the motion of the sun which we see, but by the shining of the Sun of righteousness upon our souls; not by the celestial bodies, but by the celestial inspirations. Think that a long time wherein there were many days of grace, and mind that time and improve it above all the rest....A day of grace, a Lord's day, when God shall move upon our souls, such an opportunity as this, if God affect our hearts, is worth all our days beside, when we are left unto ourselves....Let us therefore employ such time well, and set ourselves to our business, earnestly entreating more of such time, and that God's Spirit will visit us more frequently with its company....We must value time hereafter as mariners do at sea, by the win that blows upon us, and then we most [hoist] up our sails. We must look at some as harvest days, and then we must gather and lay up in store by hard labour: or as market days, and then we must buy what we want, and lay in provision for the following days. Yea, the blackest day of affliction, if we were well skilled, might be numbered among the best times of our life; for God chasteneth us for our profit, that we may be made partakers of his holiness.