There are certain regions where sun rays cannot reach due to weather effect. In such case, how can one distinguish between a night and a day? How are we supposed to follow the vow of “रात्रि भोजन त्याग”?
As per my understanding, रात्रि भोजन is considered as per the sunrise & sunset time (including the time when the food is cooked & the utensils are washed). The sunset/sunrise time is calculated as per the ज्योतिष विज्ञान.
So even if there is enough sunrays but time exceed the sunset time, we must not eat and we should make sure that there are enough natural sunrays (not necessarily direct) to properly check and consume the food. Consuming food in low lights is हिंसक even if the sun is shining bright outside.
Remember the story of the Jackal (not sure if सम्यक्त्वी) who took the vow of रात्रि भोजन त्याग by a monk, went down in stepwell to drink water, found no sunrays so came back up and saw sunrays so again went down… keep doing vice versa, later died and became देव. Later, he also became राम.
What if we use artificial lights (bulb, tube lights etc)? Only sunrays are capable of creating an environment where insects & living organisms can’t take birth. It’s clearly visible that lots of flying insects revolve around a bulb in the night and not at all during daytime.
Rest, as per the situations, we should take decisions. If hard to form any decision, do एकासन.