- Adar I and Adar II Overview for the 5787 Jewish Leap Year
- Why the Jewish Calendar Has Leap Years and 13-Month Cycles
- When Is Purim Celebrated in a Leap Year?
- Hebrew Birthdays and Bar Mitzvahs in Adar I and Adar II
- Observing Yahrzeits During a 13-Month Year
- How Digital Tools Calculate Leap Year Dates
- Frequently Asked Questions
- The Bottom Line
Adar I and Adar II Overview for the 5787 Jewish Leap Year
Quick answer: During the 5787 Jewish leap year, the calendar inserts an extra 30-day month, resulting in adar i and adar ii. Adar I serves as the added month, while Adar II hosts the holiday of Purim on March 23, 2027, along with major milestone observances.
The Jewish year 5787, which began at sunset on Rosh Hashanah on September 12, 2026, is designated as a Shanah Me’uberet, a leap year on the Hebrew calendar. Unlike the civil Gregorian calendar that inserts a single extra day (February 29) every four years, the Jewish calendar inserts a complete 30-day month. This results in two consecutive months named adar i and adar ii during late winter and early spring.
Adar I, also known as Adar Aleph or Adar Rishon, is the extra month inserted prior to the standard Adar. Adar II, also known as Adar Bet, Adar Sheni, or V’Adar, functions as the primary Adar for major festival observances. Understanding how these two months operate helps families schedule lifecycle events, commemorative anniversaries, and holiday observances accurately throughout 2027.
Because adding a 30-day month shifts subsequent spring and summer holidays roughly a month later on the Gregorian calendar, spring festivals in 2027 arrive later in April and June than in non-leap years. Exploring our master Jewish calendar guide provides a full overview of month structures, seasonal alignments, and leap year cycles.
Why the Jewish Calendar Has Leap Years and 13-Month Cycles
The necessity of adding Adar I and Adar II stems from the lunisolar nature of the Hebrew calendar. While solar calendars follow the 365-day solar tropical year, lunar calendars base their months on the 29.5-day synodic cycle of the moon. Twelve lunar months equal roughly 354 days, creating an annual discrepancy of approximately 11 days compared to the solar year.
Without periodic correction, lunar months would drift backward through the solar seasons over time. Biblical law mandates that Passover must always occur in the spring season (Chodesh HaAviv) and that harvest festivals align with their corresponding agricultural seasons in Israel. To prevent seasonal drift, the Jewish calendar employs a 19-year astronomical cycle known as the Metonic cycle.
Within every 19-year cycle, 7 years are designated as leap years: years 3, 6, 8, 11, 14, 17, and 19. Hebrew year 5787 represents year 11 in the current 19-year cycle. Adding a 13th month during these 7 designated years reconciles the lunar months with the solar year, ensuring that festivals remain anchored in their proper seasons perpetually.
When Is Purim Celebrated in a Leap Year?
One of the most frequent questions during a leap year concerns the exact timing of Purim. In a regular 12-month year, Purim is celebrated on the 14th day of Adar. In a 13-month leap year, the main celebration of Purim takes place in Adar II, while a minor observance called Purim Katan occurs in Adar I.
In 5787, Purim Katan (Little Purim) is observed on the 14th day of Adar I, which corresponds to Sunday, February 21, 2027. Purim Katan is marked by omitting fasting and penitential prayers (Tachanun) and holding festive meals, though public Megillah readings and gift exchanges are reserved for the main holiday in Adar II.
The full festival of Purim is celebrated on the 14th of Adar II, beginning at sunset on Monday, March 22, 2027, and continuing through Tuesday, March 23, 2027. Shushan Purim, observed in walled cities such as Jerusalem, falls on Wednesday, March 24, 2027. All primary Purim mitzvot, including hearing the Megillah read, distributing food gifts (mishloach manot), giving charity to the poor (matanot la’evyonim), and enjoying a festive feast, take place during Adar II.
Hebrew Birthdays and Bar Mitzvahs in Adar I and Adar II
Lifecycle events occurring in Adar require careful calculation during a 13-month year. How a Hebrew birthday or bar mitzvah is observed in a leap year depends on whether the individual was originally born in a regular year or in a leap year.
- Born in Adar during a regular year: When a leap year arrives, common custom observes the annual Hebrew birthday during Adar II. However, some Sephardic and Ashkenazi communities observe or acknowledge Adar I as well. Presenting both traditions respectfully is standard practice among community authorities.
- Born in Adar I during a leap year: For someone born in Adar I during a previous leap year, their Hebrew birthday in 5787 is celebrated during Adar I.
- Born in Adar II during a leap year: For someone born in Adar II during a previous leap year, their Hebrew birthday in 5787 is celebrated during Adar II.
- Bar and Bat Mitzvah Milestones: A boy born in Adar during a regular year who turns 13 during a leap year reaches religious adulthood on his Hebrew birth date in Adar II by widespread rabbinic consensus.
To determine exact Hebrew birthday dates or bar mitzvah milestones for any year, enter your civil birth details into our free Jewish birthday calculator, which accounts for leap years automatically.
Observing Yahrzeits During a 13-Month Year
Yahrzeit, the annual anniversary of a relative’s passing, is observed with a 24-hour memorial candle, Kaddish recitations, and Torah study. During a leap year containing Adar I and Adar II, determining the correct yahrzeit date depends on traditional authority guidelines and community origin.
| Original Date of Passing | Observance in a Leap Year (5787) | Customary Practices & Guidelines |
|---|---|---|
| Adar in a non-leap year | Adar II (Most Ashkenazi / Sephardic) | Many observe primarily in Adar II; some Ashkenazim light candles and say Kaddish in both Adars. |
| Adar I in a previous leap year | Adar I | Anniversary is strictly observed in Adar I during subsequent leap years. |
| Adar II in a previous leap year | Adar II | Anniversary is strictly observed in Adar II during subsequent leap years. |
| Any other month (e.g., Kislev, Tevet) | Normal Hebrew date | Observed on its standard date; the extra month extends the interval between annual anniversaries. |
Because custom varies regarding whether Yahrzeit for someone who passed away in Adar during a non-leap year is observed in Adar I, Adar II, or both, consulting your family rabbi ensures adherence to your community’s specific custom. For converting dates of passing into Hebrew calendar dates, use our automated Jewish date converter tool.
How Digital Tools Calculate Leap Year Dates
Manually calculating leap year dates, milestone anniversaries, and weekly Shabbat start times across 13 months can be complex. Mathematical algorithms convert lunar and solar parameters, applying rules like postponement rules (Dehiyot) that govern the Hebrew calendar.
Automated digital tools handle these complex leap year calculations effortlessly behind the scenes. Whether calculating the exact Hebrew date for a wedding, checking Purim dates, or determining weekly Sabbath candle times, modern calculators eliminate human error and guesswork.
For example, if you need weekly candle lighting schedules that account for seasonal shifts across 13 leap year months, check out our guide on what time does Shabbat start to maintain accurate Friday schedules throughout the year.
Frequently Asked Questions
Which month is added in a Jewish leap year?
Adar I is inserted into the calendar as the extra 30-day month prior to Adar II during leap years.
When is Purim celebrated in a leap year?
The main holiday of Purim is celebrated during Adar II, while Purim Katan is noted in Adar I.
How often does a Jewish leap year occur?
Leap years occur 7 times in every 19-year Metonic cycle to keep lunar months aligned with solar seasons.
If I was born in Adar, when is my birthday in a leap year?
By widespread custom, someone born in Adar during a non-leap year celebrates their birthday in Adar II.
The Bottom Line
The presence of Adar I and Adar II in 5787 demonstrates the brilliant design of the lunisolar Jewish calendar. By adding an extra month, the calendar ensures that Purim, Passover, and all sacred holidays remain beautifully synchronized with the natural solar seasons.
To convert dates, check milestone anniversaries, and explore upcoming holiday schedules across leap years, visit our master guide or use our digital converters for complete peace of mind.
