C.S. Lewis - " If you picture time as a straight line along which we have to travel, then you must picture God as the whole page on which the line is drawn. We come to the parts of the line one by one: We have to leave A behind before we get to B, and cannot reach C until we leave B behind. God, from above or outside or all around contains the whole line and sees it all." ( Mere Christianity)

Our "measurement" of time (seconds, minutes, hours, days, weeks, months, years, decades, centuries, millennia) is loosely based on the speed of the Earth's rotation and the speed of our orbit around the sun.
A "year" on Jupiter is 11.86 earth years. A "day" on Jupiter is only 9.85 earth hours. There are approximately 10500 Jupiter "days" in a Jupiter "year". If you change your location then you may change your measurement of time BUT time is still the same on Jupiter.

The first known calendar system was actually the lunar calendar which followed the cycle of the moon. Creation of a lunisolar calendar created a need to add a "leap month" every few years to keep the seasons in sync with a "year". We now mostly use an entirely solar based calendar and we have the same issue to a smaller degree today with the "leap year".
 
As usual, when I go looking for answers about something I tend to just find more questions. When that happens there is one place I can always find some comfort and conclusion. This is some of what the Bible has to say about time:

But do not forget this one thing, dear friends: With the Lord a day is like a thousand years, and a thousand years are like a day. (2 Peter 3:8 NIV)
A thousand years in your sight are like a day that has just gone by, or like a watch in the night. (Psalm 90:4 NIV)
 
To every thing there is a season, and a time to every purpose under the heaven: A time to be born, and a time to die; a time to plant, and a time to pluck up that which is planted; A time to kill, and a time to heal; a time to break down, and a time to build up; A time to weep, and a time to laugh; a time to mourn, and a time to dance; A time to cast away stones, and a time to gather stones together; a time to embrace, and a time to refrain from embracing; A time to get, and a time to lose; a time to keep, and a time to cast away; A time to rend, and a time to sew; a time to keep silence, and a time to speak; A time to love, and a time to hate; a time of war, and a time of peace. (Ecclesiastes 3:1-8 KJV)
 
He has made everything beautiful in its time. He has also set eternity in the human heart; yet no one can fathom what God has done from beginning to end. (Ecclesiastes 3:11 NIV)

Do not boast about tomorrow, for you do not know what a day may bring. (Proverbs 27:1 NIV)
 
Therefore do not worry about tomorrow, for tomorrow will worry about itself. Each day has enough trouble of its own. (Matthew 6:34 NIV)
 
Why, you do not even know what will happen tomorrow. What is your life? You are a mist that appears for a little while and then vanishes. (James 4:14 NIV)
 
Now, brothers and sisters, about times and dates we do not need to write to you, for you know very well that the day of the Lord will come like a thief in the night. (1 Thessalonians 5:1, 2 NIV)
 
We try and understand and control things that are beyond our understanding and out of our control. Time is out if our control and as much as we'd like to deny it we really do not understand it either. My simple conclusion is this: time is a gift from God! We don't have to understand it but I hope and pray that the time God has given me is something that I enjoy rather than worry about, that I don't take for granted, and that I use wisely for the purposes He intended.