I can tell you that here in the future, we expect proper data, just as they did back in 2010 (and 1910 and 1810, etc.)Proper data has an explanation for each line. Does your list represent readings at 1min, 2min, etc? Then say so. Even back in 2010, not doing so was called "unlabeled".Proper data is concise. It does not include the same number represented as seconds and milliseconds. Even back in 2010 repeating values was called "redundant".
I'm thinking of using a DS3231 (like a chronodot) to create an accurate 1Hz interrupt on the Arduino.
I'm seeing unacceptable timing errors for anything more accurate than an egg timer.