30 lines
1.2 KiB
TypeScript
30 lines
1.2 KiB
TypeScript
/**
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* Formats a JS Date as an ISO 8601 string carrying its actual Europe/Berlin
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* UTC offset (e.g. "2026-06-15T09:00:00+02:00" in summer,
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* "...+01:00" in winter) - what schema.org's Event startDate/endDate
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* expect. Uses Intl's timezone database rather than hardcoded +1/+2 math,
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* so it's correct across the DST transition automatically.
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*/
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export function toBerlinOffsetISOString(date: Date): string {
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const parts = new Intl.DateTimeFormat("en-US", {
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timeZone: "Europe/Berlin",
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year: "numeric",
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month: "2-digit",
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day: "2-digit",
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hour: "2-digit",
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minute: "2-digit",
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second: "2-digit",
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hourCycle: "h23",
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timeZoneName: "shortOffset",
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}).formatToParts(date);
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const get = (type: string) => parts.find((p) => p.type === type)?.value ?? "00";
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const tzName = parts.find((p) => p.type === "timeZoneName")?.value ?? "GMT+0";
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const match = /GMT([+-])(\d+)(?::(\d+))?/.exec(tzName);
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const sign = match?.[1] ?? "+";
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const offsetHours = (match?.[2] ?? "0").padStart(2, "0");
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const offsetMinutes = (match?.[3] ?? "0").padStart(2, "0");
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return `${get("year")}-${get("month")}-${get("day")}T${get("hour")}:${get("minute")}:${get("second")}${sign}${offsetHours}:${offsetMinutes}`;
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}
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