We can now measure time more accurately than in the past (see this question). What are the implications? I do not ask about situations where the time is critical for a Torah law where obviously one should make sure that the time chosen is in the permitted zone.
But consider for example the time for Honetz Hachamah on a day when the sun is not visible. In earlier times, assume this time could have determined to within 5 minutes. My question is whether I have to time my Amidah to the nearest minute on my clock or whether I can rely on the practice of earlier times and within 5 minutes either side would be still constitute tefillo at Honetz Hachamah.