I don't suggest one is right, the other wrong, or that one corrects the other, only that the Psalm gives us two different methods for measuring "God's time" and both can only correct if "God's time" is indefinite in our terms.
You disagree?
Does not the calculation of a day, not also include the night? Even to this day? I am puzzled that there is a suggestion the words of David in anyway change what Peter wrote. It seems many do not believe Christ when He declared in Mark 13:23 "But take ye heed: behold, I have foretold you all things." This would include the meaning and purpose for the instruction on how God marks time.