Shavuot date calculator by Gregorian year

It computes the result from the fixed arithmetic rules of the Hebrew calendar, including leap years, lunar conjunction calculations, New Year postponements, and variable month lengths. No current clock, timezone, online calendar, or external lookup table affects the answer. Enter a year and receive an ISO-formatted Gregorian date together with the corresponding Hebrew year and Hebrew date, making the result convenient for schedules, records, software tests, and historical research.

What the Shavuot date result means

Shavuot begins on 6 Sivan in the Hebrew calendar, but its Gregorian date changes from year to year because the two calendars organize time differently. The Hebrew calendar combines lunar months with a nineteen-year leap cycle, while the Gregorian calendar follows a solar year with its own leap-day rules. This calculator accepts the Gregorian year in which the observance occurs and returns the matching civil date in ISO format, along with separate month and day values. It also reports the Hebrew year and the conventional Hebrew label, such as 6 Sivan followed by the year number. The result identifies the calendar date, not a location-specific candle-lighting time or service time. Jewish dates begin at sunset, so an observance ordinarily starts on the evening before the returned Gregorian daytime date. Local practice, diaspora observance, and event scheduling can affect how long a community marks the holiday, but they do not change the computed date of 6 Sivan itself.

How arithmetic Hebrew calendar rules produce the date

The calculation starts by mapping the requested Gregorian year to the Hebrew year whose spring contains Shavuot. It then counts lunar months elapsed before that Hebrew year according to the fixed nineteen-year cycle. From those months it derives the traditional mean conjunction, or molad, of Tishri in days, hours, and parts. The algorithm applies the standard postponement rules that prevent Rosh Hashanah from occurring on certain weekdays and handle conjunctions that fall too late or create unsuitable neighboring year lengths. The distance between consecutive Hebrew New Years determines whether Cheshvan and Kislev are short, regular, or long in that particular year. After accounting for an added Adar in leap years, the calculation advances to 6 Sivan. Finally, a pure integer Gregorian conversion turns the resulting fixed day count into a year, month, and day. Every operation depends only on the supplied integer, so repeated calls produce identical output regardless of machine locale, timezone, clock, or daylight-saving setting.

Using the date safely in calendars and applications

Use the ISO date field when you need a stable value for a database, calendar generator, reminder system, editorial schedule, or automated test. Because the returned string has year, month, and day in descending order, it sorts naturally and avoids ambiguity between month-first and day-first regional formats. Keep the Hebrew fields when an audit trail should explain why that civil date was chosen. If your application displays the start of the holiday, label the preceding evening appropriately instead of subtracting an assumed number of hours: sunset depends on coordinates and requires a separate astronomical calculation. Likewise, this capability does not decide whether a user observes one day or two days, nor does it provide readings, liturgy, or work-restriction guidance. It answers one narrow calendar question reproducibly. For batch planning, call it once per Gregorian year and store the output. The API price is $0.002 per request, while the browser version can perform the same deterministic calculation locally without sending calendar input elsewhere.