Error in day length calculation

[AnttiRumpunen]

Check how day length is calculated.

fmi.fi uses the following codes

 async function fetchDayLengthValues(geoid, timezone) {
    const now = new Date();

    // Substract one hour, because timeseries returns the next even hour with Sunrise and Sunset
    // This means that whenever time would be for example 23:01 localtime, it would return
    // 00:00 values, which are already the sunrise and sunset values for the next day.
    // This way we get the correct values for the current day, because it changes to return the
    // previous even hour values.
    now.setHours(now.getHours() - 1);

    // Use swedish locale with selected place timezone. Sweden uses timeseries compliant ISO-8601 standard
    const formattedStartTime = now.toLocaleString('sv-SE', { timeZone: timezone });

    const params = {
      param: 'Sunrise,Sunset',
      starttime: formattedStartTime,
      format: 'json',
      geoid,
      tz: timezone,
      timesteps: 1,
      who: 'wau2-api',
    };

    let data = [];
    try {
      const start = process.hrtime();
      const response = await axios.get(getTimeseriesUrl(), {
        params,
      });
      const duration = getDurationInMilliseconds(start);
      if (process.env.ENV !== 'prod') {
        console.log(`fetchDayLengthValues [FINISHED] ${duration.toLocaleString()} ms`);
      }
      data = response.data;
    } catch (e) {
      logException(e, 'Error in loading day length values');
      // don't send error code
      return false;
    }

    return data;
  }

if (!data.Sunrise || !data.Sunset) {
      return {};
    }

    let sunriseAndSetFormat = 'H:mm';

    // length of day
    const start = parseISO(data.Sunrise);

    const end = parseISO(data.Sunset);
    const durMins = differenceInMinutes(end, start);
    const hours = Math.floor(durMins / 60);
    const minutes = durMins - hours * 60;
    let lengthofday = `${hours} h ${minutes} min`;

    if (!isSameDay(start, end) && isSameYear(start, end)) {
      // not same day, but is same year
      sunriseAndSetFormat = 'd.M. H:mm';
      lengthofday = null;
    } else if (!isSameYear(start, end)) {
      // not same year
      sunriseAndSetFormat = 'd.M.yyyy H:mm';
      lengthofday = null;
    }

    // format sunrise and set
    const sunrise = data.Sunrise ? format(start, sunriseAndSetFormat) : '-';
    const sunset = data.Sunset ? format(end, sunriseAndSetFormat) : '-';

    return {
      sunrise,
      sunset,
      lengthofday,
    };