Du nutzt offenbar einen modifizierten Code von jurs
Der orginale Code von jurs schaut wohl so aus:
/*-------- utility code from jurs ----------*/
boolean summertime_EU(int year, byte month, byte day, byte hour, byte tzHours)
// European Daylight Savings Time calculation by "jurs" for German Arduino Forum
// input parameters: "normal time" for year, month, day, hour and tzHours (0=UTC, 1=MEZ)
// return value: returns true during Daylight Saving Time, false otherwise
{
if (month<3 || month>10) return false; // keine Sommerzeit in Jan, Feb, Nov, Dez
if (month>3 && month<10) return true; // Sommerzeit in Apr, Mai, Jun, Jul, Aug, Sep
if (month==3 && (hour + 24 * day)>=(1 + tzHours + 24*(31 - (5 * year /4 + 4) % 7)) || month==10 && (hour + 24 * day)<(1 + tzHours + 24*(31 - (5 * year /4 + 1) % 7)))
return true;
else
return false;
}