Working out with an ever changing schedule

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Hey, so I currently work in retail store (hopefully will be able to get out in a little while) but I can work anywhere between 7:30am and 8pm, everyday is a changing schedule and everyweek is different. I'm curious to any one that had a similar type of schedule, How? How'd you work out? I have attempted to get up at 6am and get an hour in or something like that, but haven't been able to keep it up, and as it's never the same time of the day I cannot keep it into a routine, any tips?