func RelativeDate(days int, hour int) time.Time {
	now := time.Now().UTC().AddDate(0, 0, days)
	return time.Date(now.Year(), now.Month(), now.Day(), hour, 0, 0, 0, time.UTC)
}
RelativeDate returns a date in the future in specified days and hours.
This allows running the tests in parallel, since each tests uses different date and hour.

The downside of this approach is that you need to be aware of used dates when adding a new test.
In our case this is not an issue, as it's trivial to see all usages and there's just a few of them.

Another, more complex approach, would be to use random dates and retry in case of an error.
package tests
import "time"