Thirteen months. Every day still counts.
The first twelve months each have 28 days: exactly four seven-day weeks. Together they account for 336 days. The final month, Telara, holds the days remaining before the next New Year.
The remainder
MATHEMATICAL CONSEQUENCE
12 × 28 = 336. A 365-day year leaves 29 days for Telara; a 366-day year leaves 30.
Every day belongs to a month and a weekday. There is no extra day outside the week.
The name Pleroman draws on pleroma, associated with fullness or completeness. Telara is a modern coined name inspired by the idea of completion; it is not an ancient Greek word.
Why begin with the March equinox?
The aim is to connect each New Year directly to a recurring event in the Earth's seasonal cycle. The March equinox is the chosen anchor. It marks spring in the Northern Hemisphere and autumn in the Southern Hemisphere; this is a solar calendar, not a calendar governed by Moon phases. USNO explains the seasonal events.
An equinox instant is calculated first using an astronomical model. A single reference rule then assigns it to a date at Greenwich using UT1, a measure of time tied to Earth's rotation. That reference date is called Pleroman March 1 everywhere.
Your ordinary day still starts at local midnight. New Year's Day does not begin at the precise instant of the equinox, and your location does not choose a different calendar structure.
Instead of a separate arithmetic leap-year rule, the number of days between consecutive New Year dates determines Telara's length. This moves the problem of maintaining seasonal alignment into the astronomical calculation and its reference rules. It does not remove the need for careful timekeeping.
What would feel familiar? What would change?
Monday still follows Sunday. The day itself does not move when its calendar label changes. The familiar year number is retained: Pleroman 2026 begins at the March-equinox reference date in Gregorian 2026 and continues into Gregorian 2027.
MATHEMATICAL CONSEQUENCE
Because 28 is divisible by seven, every month starts on the same weekday within a given year. The pattern for dates 1–28 repeats across all thirteen months. The next year's pattern advances by one weekday after a 365-day year, or two after a 366-day year.
Familiar month names have different boundaries. Pleroman January is month 11, and Pleroman September is month 7. A birthday or appointment needs its calendar identified clearly.
| Gregorian date | Pleroman date | What it illustrates |
|---|---|---|
| March 20, 2026 | March 1, 2026 | The start of the year |
| September 19, 2026 | September 16, 2026 | Same day, a different label |
| December 25, 2026 | January 1, 2026 | The month name does not preserve its Gregorian dates |
| March 19, 2027 | Telara 29, 2026 | The Pleroman year has not changed yet |
Try your own date in the converter. The table describes date conversion, not a proposal to relocate holidays. The app's holiday overlays retain their stated Gregorian or liturgical rules.
Regularity brings possibilities—and tradeoffs.
The design aims to make most months easier to compare and to place annual variation in one predictable location. Whether that improves planning, work, or everyday life needs practical study.
What the structure offers
- Twelve months of equal length.
- A repeating monthly weekday pattern within each year.
- Continuous weeks across every boundary.
- A defined seasonal reference for New Year.
What still needs working out
- Thirteen months do not divide into four equal groups of whole months.
- Telara is longer than the other months.
- Pay periods, contracts, school years and holidays would need transition decisions.
- Future astronomical predictions need a policy for uncertainty and revisions.
Those questions are not solved by a working date converter. The present proposal defines a calendar architecture; it does not establish that society should replace its existing calendar.
Regular months, thirteen-month arrangements and seasonal year boundaries have precedents. Pleroman's proposal concerns their particular combination. The initial proposal discusses historical comparisons; it is not evidence that Pleroman is historically unprecedented or preferable.
A proposal you can examine.
The calendar rules are set out in a working technical specification, version 0.1. The site implements one astronomical method and publishes a record of checks on that implementation. Internal consistency, external astronomical agreement, independent reproduction and practical usefulness are different questions.
The optional historical and religious overlays are separate research or conventional-event layers. They do not establish disputed historical dates and do not determine the civil calendar's mechanics.
You can use the calendar, read the reasoning, or challenge its assumptions. A disagreement is useful when the date, rule, source and reasoning can be inspected.