God exists in three ways simultaneously. If His existence comprehends past, present and future simultaneously, God is able to exist in ways that seem paradoxical to us. If this is true of time; it may be equally true of personhood.
“The Trinity is in the Old Testament present but concealed; The Trinity is in the New Testament present and revealed.” True enough, and equally true of how much the covenant name of God reveals of the Trinity in the respective Testaments.
When Moses first learns God’s name, there is something implicit in the conversation that implies threeness. Having heard God announce that He is Ehyeh Asher Ehyeh—I AM THAT I AM—the announcement of God’s name with the Hebrew consonants YHVH would have made Moses recognise that God’s name had to do with existence and being, and yet it was a new Hebrew word. God does not simply call Himself Ehyeh (I AM). Instead, God gives Moses a new Hebrew word that appears to be a concatenation of syllables from three other words: Yihyeh—He will be; Hoveh—He was; Hayah—He is. Moses would have heard in the word a strange future/past/present participle mixture. All three Hebrew tenses or aspects combine into one name. God is: in the future, the past, and the present.
This was implicit and concealed in the Hebrew name. But when the beloved disciple, John, writes the New Testament book of Revelation, he is happy to bring his Hebrew knowledge of the Name to his Greek readers. Instead of merely transliterating the name into a Greek form, something like “Ieova”, John translates the name altogether.
“Grace to you and peace from Him who is and who was and who is to come”
Revelation 1:4