2 Peter 3:8

But be not ye ignorant — Whatever they are. Of this one thing — Which casts much light on the point in hand. That one day is with the Lord as a thousand years, and a thousand years as one day — Moses had said, Psalms 90:4, "A thousand years in thy sight are as one day;" which St. Peter applies with regard to the last day, so as to denote both his eternity, whereby he exceeds all measure of time in his essence and in his operation; his knowledge, to which all things past or to come are present every moment; his power, which needs no long delay, in order to bring its work to perfection; and his longsuffering, which excludes all impatience of expectation, and desire of making haste. One day is with the Lord as a thousand years — That is, in one day, in one moment he can do the work of a thousand years. Therefore he "is not slow:" he is always equally ready to fulfil his promise. And a thousand years are as one day — That is, no delay is long to God. A thousand years are as one day to the eternal God. Therefore "he is longsuffering:" he gives us space for repentance, without any inconvenience to himself. In a word, with God time passes neither slower nor swifter than is suitable to him and his economy; nor can there be any reason why it should be necessary for him either to delay or hasten the end of all things. How can we comprehend this? If we could comprehend it, St. Peter needed not to have added, with the Lord.