Why do our dates differ from the Hebrew Calculated Date (HCD)?
The modern rabbinical calendar (HCD), fixed by Hillel II around 359 CE, bakes Saturday into the system as a fixed weekly Sabbath. Because of this, it introduces postponement rules (dehiyyot) that shift the start of months to prevent holy days from falling on certain weekdays. Month lengths for Cheshvan and Kislev are adjusted, and Rosh Hashanah is moved if it would land on Sunday, Wednesday, or Friday—all to protect the Saturday Sabbath cycle from conflicts.
This calendar does not honor Saturday as the Sabbath. Instead, the Sabbath cycle resets with each new moon, as Isaiah described—from new moon to new moon and Sabbath to Sabbath. With no fixed weekday Sabbath to protect, there is no need for postponements or month-length adjustments. Months follow a consistent 30/29-day alternating cycle anchored by the new moon. The full moon opposition on the evening of day 14—when the sun and moon appear on opposite horizons at sunset—confirms the month is in sync. The result is a calendar that can differ from the HCD by one to two days in any given month.
A lunar year of 12 months (~29.5 days each) totals roughly 354 days—about 11 days short of a solar year. Without correction, the months drift backward through the seasons. The 19-year Metonic cycle solves this: 235 lunar months fit almost exactly into 19 solar years. Within each cycle, 7 of those years (positions 3, 6, 8, 11, 14, 17, 19) receive a leap month—a full 30-day Adar I inserted before the regular Adar (which becomes Adar II at 29 days). This realigns the lunar months with the solar year and keeps Aviv (Passover) in the spring. It intentionally breaks the alternating 30/29-day pattern—Shevat (30 days) is followed by Adar I (30 days), placing two 30-day months back to back before Adar II (29 days) restores the cycle. The moon and sun do the math; no human adjustment is required.
Gregorian date offset: Each Hebrew day begins at evening (sunset), not midnight. This means every lunar day overlaps two Gregorian dates—the evening of one and the daytime of the next. The Gregorian date shown on each day block represents the daytime portion. The actual overlap shifts throughout the year with sunset times and daylight saving, but we estimate roughly 30% of the lunar day falls on the previous Gregorian date.
This page invites you to rediscover time as revealed through the prophet Isaiah: "From new moon to new moon and from Sabbath to Sabbath, all flesh shall come to worship before me, says the Lord" (Isaiah 66:23). This vision of worship aligns with a calendar anchored in the cycles of the moon, embracing the original Sabbaths and holy days as God intended from creation.
By aligning each month from new moon to new moon, this calendar reflects the divine rhythm in which Sabbaths are not arbitrary but are intentionally placed by celestial markers. This system—known here as the Joshua Way—presents a return to an ancient understanding of sacred time, where worship and rest align with the natural order established by the Creator.