Inversing sign for timezone offsets with half hour intervals

Asked Oct 05 '22 at 07:09

Active Oct 05 '22 at 07:30

Viewed 52 times

I'm using ideas from this implementation to get time zone offset, but because of standard defined inversion logic for offsets the code looks like this:

  const [, sign, hour, minute] = matchData;
  let result = parseInt(hour) * 60;
  if (sign === '+') result *= -1;
  if (minute) result += parseInt(minute);

and for the Asia/Kolkata with offset +5:30 it returns -270, which is weird. I'd expect it to be -1 * (5*60 + 30) = -330, or even more intuitive not inverted value 5*60 + 30 = 330, but not -270.

Is this the error or is it consistent with the standard?

edited Oct 05 '22 at 07:20

asked Oct 05 '22 at 07:09

Max Koretskyi

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Just incase if you missed it, -1 * 5 * 60 + 30 is -270, not -330 – Sathwik Gangisetty Oct 05 '22 at 07:19
yeah, added paranthesis – Max Koretskyi Oct 05 '22 at 07:20
Just swap the two "if" to get -330 – Astor Oct 05 '22 at 11:00
@Astor, so do you think it's an error in the original implementation? – Max Koretskyi Oct 05 '22 at 12:16
Yes @MaxKoretskyi, in the code that you posted, you change the sign (*= -1) and after you add the minutes (+30) so you get -270. If you swap the two lines of the "if"s, you will get -330 – Astor Oct 08 '22 at 13:58
@Astor, yeah, I understand that, just wondering if it was intentional – Max Koretskyi Oct 09 '22 at 07:18
No idea about the intention, but the original code does not return the value that you need :) – Astor Oct 18 '22 at 15:20

Inversing sign for timezone offsets with half hour intervals

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