Riddle me this. #1

[center][c=1F5E00]I am the shadow that follows you around,[/c]
[c=800055]With every step, my presence is found.[/c]
[c=359E00]I'm the one thing you cannot escape,[/c]
[c=7700B2]No matter how fast or how far you make.[/c]
[c=004A59]From the moment you're born, I am near,[/c]
[c=BF6900]Ticking away with every passing year.[/c]
[c=A69800]Inevitable, undeniable, my fate,[/c]
[c=BF0080]Your time with me is never up for debate.[/c]

[b][big]What am I?[/b][/big][/center]