Working with time is tricky. It's not hard. But speeding it up so the workday isn't as long results in a very, very, very long shift the next day. Or worse, on a Saturday when you really didn't want the overtime. So just be aware that you can speed time up, or slow it down, but time will 'reset' itself later.
Going back in time is very different. You can change the past. You can erase events from your space/time continuum. Whether or not this has ill effects depends on what you erased and why.
A couple of years ago I cast a heal the past spell. My mother's family was so bitter. I went back in time and imagined my grandparents had a happy marriage. Now I don't know what troubles they had other than neither was happy with the other. So I just began envisioning them as pleasant in each other's company. Then I moved on to imagining them as happy together.
The result was that my mother can now tolerate her sisters. One she now talks to every day. I didn't try to erase bad things from my mother's life. But now she no longer dwells on things from her past. She doesn't complain about her family anymore. She's not angry anymore.
Time can be bent with mirrors. I've read about this but never actually tried it. Three mirrors are needed and they must be positioned so that in turn they reflect the one before. The second reflects the first mirror and the third reflects the second. A hallway works well for placement. If you set this up correctly and stand at the end of the hall you should be able to see the past.
There's a couple of problems.
How far back in time can you go? Is this determined by the size of the mirrors or the distance between them? How to go back to a particular date rather than any random point? When exactly does the time bending start- instantly or after a few days? Or is that the way to determine how far back into the past? What if I see an event and I want to stop it like a video tape? What if someone walks down the hall, does it start over, continue on, or does the event become shaped by whoever walked by?
I need to figure these things out. I have work to do.