And Jesus said to him, “Assuredly, I say to you,
today you will be with Me in Paradise.” - Luke 23:43
http://www.biblegateway.com/passage/?search=Luke23:43&version=NKJV
Jesus said "today" the thief would be with him in heaven.
Not a week from then, not a month, year, decade, century, or millenium. "Today."
How long after he said that until the end of that day? I would imagine only a few hours.
You're thinking: "Oh, but what about 2 Peter 3:8? I've got you there."
But, beloved, do not forget this one thing, that with the Lord one day is as a thousand years, and a thousand years as one day. - 2 Peter 3:8
http://www.biblegateway.com/passage/?search=2Peter3:8&version=NKJV
Before you go there, you should probably look at what the context of the verse is, and to do that, you should read the verses before and after it. I'll quote them here for you:
Beloved, I now write to you this second epistle (in both of which I stir up your pure minds by way of reminder),that you may be mindful of the words which were spoken before by the holy prophets, and of the commandment of us, the apostles of the Lord and Savior,knowing this first: that scoffers will come in the last days, walking according to their own lusts,and saying, “Where is the promise of His coming? For since the fathers fell asleep, all things continue as they were from the beginning of creation.”For this they willfully forget: that by the word of God the heavens were of old, and the earth standing out of water and in the water,by which the world that then existed perished, being flooded with water.But the heavens and the earth which are now preserved by the same word, are reserved for fire until the day of judgment and perdition of ungodly men.
But, beloved, do not forget this one thing, that with the Lord one day is as a thousand years, and a thousand years as one day. The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish but that all should come to repentance. - 2 Peter 3:1-9
http://www.biblegateway.com/passage/?search=2Peter3:1-9&version=NKJV
Note verse 9:
"The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish, but that all should come to repentance."
"The Lord is not slack. . . but is longsuffering toward us".
So what is being discussed? God's patience and capability.
"One day is as a thousand years, and a thousand years as a day" is talking about God's patience towards humanity and that He is extraordinarily capable, not about how He experiences time. God is love, and love is patient. He is, as verse 9 states, "longsuffering towards us."
If this verse meant that God is outside of time, patience is one of the many things that God could not have.
The verse also shows us that God is extraordinarily capable, doing in a single day what men may think would take eons, for instance, stretching out the heavens (on a Wednesday, btw).
The answer to my question above is this:
The thief on the cross next to Jesus was with Jesus that very day in heaven.