This post has reference to two other posts that I think will be very useful. Start there and let me know if you have questions.
Once you have a normal start date column created from the math column, then you can add the appropriate value in another math column to get the end date. Date math in glide is based on days. To add a day, to a date you simply add one. If you want to add hours or minutes, then you need add the corresponding decimal value. Each hour is ~0.0416666 (or 1/24). Each minute is ~0.00069444 (or 1/1440).
In the end you will have a start and end date that are true dates, so it will be easy to sort, filter, and query based on those dates instead of having to convert to integers.