For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Yes, that is why He told "I am who I am" Exodus 3:14. God IS present in the past, God IS present in the present and God IS present in the future. If He had said, "I am who I was", then it means that He is not present in the future. If He had said "I am who I will be", it means he was not present in the past. But He said, "I am who I am". This is the most unique and hard to comprehend sovereignity of God. He is limitless of time. Can god change what happened in the future? Yes, He can. But I dont say He will. Vice versa for the future and present. It is different. But it is evident from the book of Joshua that He has prolonged time. Daniel 7:9 mentions Him "Ancient of days". It means His being is beyond time. I.e., He is available before something called "Time" was created.
Another simple example for His omnipresence, Holy Spirit dwells within us as well as with God and as God simultaneously (2 Corinthians 3:17) Comments invited.