If we could travel backwards in time the world would be full of time travellers... Although travelling forwards is not out of question. 
All people will be rich if time could go backward...for example...i go gambling...let say yesterday arsenal vs chelsea...and its draw i put my bet in draw and ×2 my moneyif i put $1000...ill get $2000 ...easy to get rich just in one day...
Or you can just simply go back when the bitcoin was worth cents and buy tons of it then sell it 4 years after. You can be a millionaire in no time
How I really wish I knew bitcoin last 2009, too bad I only know y8.com that time