'Day' in the Bible

I thank God, whom I worship and serve with a clear conscience the way my forefathers did, as I constantly remember you in my prayers night and day,

This is why I suffer as I do. Still, I am not ashamed; for I know Him [and I am personally acquainted with Him] whom I have believed [with absolute trust and confidence in Him and in the truth of His deity], and I am persuaded [beyond any doubt] that He is able to guard that which I have entrusted to Him until that day [when I stand before Him].

the Lord grant to him that he may find mercy from the Lord on that [great] day. You know very well how many things he did for me and what a help he was at Ephesus [you know better than I can tell you].

In the future there is reserved for me the [victor’s] crown of righteousness [for being right with God and doing right], which the Lord, the righteous Judge, will award to me on that [great] day—and not to me only, but also to all those who have loved and longed for and welcomed His appearing.