Twelve months of exactly four weeks. Within each year, every date in them falls on the same weekday, month after month — and month thirteen carries the year's correction. The year begins in April when seasons are in transition, not at their extremes. HEKA Calendar is a calendar designed for clarity.
The Gregorian calendar is a stack of historical patches. Roman politics, religious councils, astronomical fixes added centuries apart. It was never designed as a coherent system.
The HEKA Calendar year flows through three distinct arcs, each serving a different purpose in the rhythm of work and rest.
The year begins at the seasonal turning — spring in the north, autumn in the south. New projects, new intentions. The threshold month.
Nine months of perfectly regular structure. Build momentum. Plan with confidence. This is where the work happens.
Bring the year to resolution. Finish what you started. Prepare for the next opening.
HEKA Calendar offers two ways to calculate the year. One keeps you aligned with the civil world. The other follows the sky itself.
March has 30 days when the next Gregorian year is a leap year. April 1st always aligns with civil April 1st. Your HEKA Calendar stays in step with the world around you.
March has 30 days every 4th year except every 128th. The calendar follows the true tropical year with astronomical precision. Your astrology aligns with the actual stars.
Switch anytime. No data is lost. Your notes, tasks, and charts adapt instantly. See the mathematics →
Six questions everyone asks about thirteen months, 28-day months, and how the HEKA Calendar handles the real world.
A 13-month calendar divides the year into thirteen months instead of twelve. In the HEKA Calendar, the year starts on April 1 and flows through twelve 28-day months — April to February — before closing with a thirteenth month, March, which holds the final one or two days of the solar year.
The first twelve months — April through February — are always exactly 28 days, four perfect weeks, every year. Only the thirteenth month, March, varies: 29 days in a common year, 30 when the next civil year is a leap year. By placing the entire correction in March, months 1–12 never change.
HEXA is the extra month that makes the calendar thirteen — the sixth month of the year, inserted between August and September. Its name comes from the Greek hex, six. Like every month from April through February, HEXA is exactly 28 days, so the middle of the year is as regular as its beginning.
Yes — within any year. Months April through February are all 28 days, so every date in them falls on the same weekday, month after month. Each new year the whole lattice steps forward one weekday — two after a correction year — because a solar year isn't a whole number of weeks; no calendar can pin weekdays across years. What the fixed grid fixes is the chaos within the year.
The solar year is about 365.25 days, so every solar calendar needs a correction. The HEKA Calendar contains it entirely in March, the thirteenth month: March has 29 days in a common year and 30 when the next civil year is a leap year. Months 1–12 never change — the whole adjustment lives in one visible place.
Yes. SYNC mode shows the civil date beside every HEKA date, so birthdays, appointments, and deadlines stay fully legible while you live on the 13-month grid — April 1st always aligns with civil April 1st. The app is in closed testing on Google Play; join via the link below.
HEKA Calendar is live on Google Play in closed testing. Join the circle and receive the Android app today, direct access to the team behind it, and a say in what ships next.
Free during testing · Android 8+ · Your data stays on your device
On iOS or desktop? Email hekacalendar@gmail.com to be notified at launch.