parse-currentTime.nix

parse-currentTime.nix

# https://stackoverflow.com/questions/7136385/calculate-day-number-from-an-unix-timestamp-in-a-math-way
# https://howardhinnant.github.io/date_algorithms.html#civil_from_days
let
  t = builtins.currentTime;
  z = t / 86400 + 719468;
  era = (if z >= 0 then z else z - 146096) / 146097;
  doe = (z - era * 146097);
  y' = (yoe) + era * 400;
  doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
  yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
  mp = (5 * doy + 2) / 153;
  day = doy - (153 * mp + 2) / 5 + 1;
  month = if mp < 10 then mp + 3 else mp - 9;
  year = y' + (if month <= 2 then 1 else 0);
in {
  inherit year month day t;
}