We all know how humanity has evolved. From stones to tablets, from Astronomy to interplanetary missions, from being hunted by animals to becoming more Powerful than them and from couting travel distance in months to seconds.
In the span of time, even the mode of keeping time has changed. From sun dials or human time keepers, we now have atomic clock accurate to the femtosecond!
Earlier, since no one could keep their own time, there came phrases like sunrise and sunset. Noon meant sun directly above your head.
People still used to keep fast. And to track that time, there must have come phrases like - you can eat after sunrise or after moon rise.
The difference between now and then is that, you can come to know when is going to be the moon rise of when has it already happened at exactly which location in earth. Thus, the practice of waiting for sun rise or sunset is purely customary according to me.
There are people who do not eat until they see the sun or the moon! The fast was meant for specific timing and as far as you can ascertain it, there is no need to wait to see the moon to break the fast. :)
