❊ Free Decennials Calculator
Umbriel computes the decennials — the Hellenistic time-lord system that divides life into periods of ten years and nine months, each subdivided among the planets in Chaldean order. Free, no account.
- What you'll needBirth date, time and place
- What you getYour full decennial sequence with major and minor periods and their dates
- CostFree — no account required
Runs in your browser. Nothing to install, nothing to set up.
What it actually is
The decennials divide life into periods of ten years and nine months — 129 months, the sum of the lesser years of the seven planets. Each major period belongs to a planet, and each subdivides into minor periods running through all seven in Chaldean order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.
That order is the technique's backbone. It is the ancient sequence of the planets by apparent speed, and it recurs throughout Hellenistic and medieval astrology — in the planetary hours, in the days of the week, and here.
Which planet opens the sequence depends on the chart and on sect, which is why two people born on the same day can be in entirely different decennial periods.
It is one of several Hellenistic time-lord systems and is usually read alongside the others rather than alone — the moment that matters tends to be where two or three of them mark the same date.
How Umbriel computes it
The decennial periods run in the Chaldean order from the ruler determined by sect and the chart's own configuration, with each ten-year-and-nine-month period subdivided proportionally into minor periods. Dates are computed from your exact birth moment rather than from your birth year, so period boundaries land on real days.
What's in your result
- The full sequenceEvery major period from birth, with dates.
- Minor periodsEach major divided in Chaldean order, with its own dates.
- Which you are in nowThe current major and minor lord.
- The rulers in your natal chartWhere each period's planet actually sits, which is what makes it readable.
- Alongside the other time lordsProfections, firdaria and releasing, so agreements between systems are visible.
Common questions
What are decennials?
A Hellenistic time-lord technique dividing life into periods of ten years and nine months, each subdivided among the seven planets in Chaldean order.
Why ten years and nine months?
It is 129 months — the sum of the lesser years traditionally assigned to the seven planets. The number comes out of the system rather than being chosen.
What is Chaldean order?
Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon — the ancient sequence by apparent speed. It also governs the planetary hours and the order of the days of the week.
Do I need a birth time?
Yes. Which planet opens your sequence depends on the chart and on whether you were born by day or night, both of which need a birth time.
How do decennials differ from firdaria and zodiacal releasing?
All three are time-lord systems and all three divide a life into planetary periods, but they use different period lengths, different starting rules and different orders. Decennials run in Chaldean order in periods of ten years nine months; firdaria runs seventy-five years over nine rulers; releasing uses the planetary years and nests four levels deep.
Should I read them alongside each other?
That is the usual practice. A single time-lord system rarely carries a reading on its own; the dates practitioners take seriously are the ones where two or three systems mark the same period independently.
Are decennials the same as the 'decanates'?
No, and the similar names cause real confusion. Decennials are periods of time; decans, or decanates, are the ten-degree divisions of a sign. One is a timing technique and the other is a way of subdividing space.
Is the decennials calculator free?
Yes — the full sequence with major and minor periods, and no account.
Go deeper
Each of these is a free tool in its own right.
Umbriel offers every system here as a set of prompts to think with, never as a statement of fact about who you are. Take what's useful, leave the rest.