If time is just a concept, what is the value of DST vs standard time? The answer is: whatever the clock says, the day rythm of society follows strongly the sun. Permanent DST will shift most time schedules in the long run. Nothing will fundamentally be changed. The disadvantabe is, "noon" will be further off the high point of the sun. Due to time zones, it was not exactly the same in most places, but with standard time the deviation is reduced. Which for example has the practical consequence, that sunrise and sunset is symmetric to noon.