Living on Satoshi Time: What Block is it?

Share this:

Today is Block Year 12, and within the year it is Block Month 5, Block Day 137

Bitcoin Generates Its Own Calendar

Our Gregorian calendar is based on the Solar year, the Lunar month, and the Terrene (Earthly) day. Bitcoin has its own natural calendar that can be constructed to approximate our human calendar of years, months, and days.

But the details are a bit different, and since Bitcoin is a dynamic process built around the construction of blocks, block count, not regular calendar time, is the most relevant and precise way of looking at the passage of time in the Bitcoin context.

Bitcoin’s fundamental process driver is the construction of a chain of blocks. Blocks are created one at a time and chained together in a time chain, or blockchain. That process and the ever-growing chain drives Bitcoin’s security and its value. The value comes both from security and scarcity, and the money supply is created on a per-block basis, via a block reward for the winning miner.

The block count is the clock. It is the system’s heartbeat. Bitcoin has its own clock that has a rough correspondence with wall clock time. Yet it has its own cycles, years, months and days of somewhat different and varying duration from regular time but with an approximate correspondence.

I now describe a natural Bitcoin calendar system, based on the block length at the short end, the difficulty adjustment in the mid-range, and the Halving cycle at the long end.

We designate block height or block number by variable B.

The first year is designated Year 1, Anno Satoshi, 1 A.S. and it originated with the first block B = 1 that was completed on 9 January 2009.

Block Year, Block Month, Block Day And More

So now let’s look at the Block Era, Block Year, Block Quarter, Block Month, Block Fortnight, Block Week, Block Day, Block Hour, and Block Minute. They are roughly equal to our familiar calendar and time intervals, but not precisely.

Bitcoin is a dynamic process creating blocks approximately, but not exactly, every 10 minutes. So BlockTime will deviate from wall clock time. There is a self-correcting process within the Nakamoto consensus algorithm that is called the difficulty adjustment, and which occurs every 2016 blocks; this is approximately every two weeks of wall clock time. Increasing or decreasing the difficulty regulates the block interval back toward 10 minutes’ duration.

The block duration and the difficulty adjustment are two of our pegs for the Bitcoin calendar system.

The most important aspect of Bitcoin’s monetary policy are the Halvings, which occur every 210,000 blocks. The block subsidy (mining reward) is cut in half after each 210,000 blocks, which also roughly equals a four-year period.

The formula for Bitcoin supply creation and Halvings, denominated in Satoshis (each Bitcoin contains 100 million Satoshis). The original reward was 50 Bitcoins with Blocks 1 through 209,999 and then cut to 25 Bitcoins from Block 210,000 through 419,999 and so forth.

No need to memorize the formula!

Formula for Bitcoin supply, with 32 Halvings at each 210,000 blocks

No need to memorize the formula!

Block, Difficulty, Halvings Define The Calendar

So these three pegs of a block (Earthly: around 10 minutes), difficulty adjustment (Lunar: around two weeks), and Halvings (Solar: around four years) allow us to define a Bitcoin calendar system.

The calendar begins with B=1 on January 9, 2009, and that initiates the Age of Satoshi. Years are rendered as A.S. (Anno Satoshi), counting begins at year one. We are now in the 12th BlockYear, the last year of the third Reward Era.

Months and weeks are numbered from 1 to 12 and from 1 to 52, respectively, within a year. Like the Gregorian calendar, there are precisely 12 months, but the calendar has slightly more than 52 weeks.

It is easy to determine the natural rhythm of the Bitcoin calendar. Rows in italics are the three pegs we build the system around.


Block Century = 5,250,000 blocks (25 Eras, 100 Block years)

Block Era (Cycle, Reward Era) = 210,000 blocks

Block Year = 52,500 blocks (one-quarter of a Block Era)

Block Quarter = 13,125 blocks (one quarter of a Block Year, or three Block Months)


Block Month = 4375 blocks (1/12 of a Block Year, and unlike Gregorian calendar, all of the equal length)

Block Fortnight = 2016 blocks (the difficulty adjustment period, and two Block Weeks)

Block Week = 1008 blocks (52 weeks plus a bit in a year, not unlike the Gregorian calendar)


Block Day = 144 blocks (1/7 of a Block Week, 24 Block Hours)

Block Hour = 6 blocks (nominal block time is 10 ordinary minutes)

Block Minute = 0.1 blocks

We can refer to these either as BitYear, BitMonth, BitWeek, BitDay, BitHour, etc.,


BlockCentury, BlockEra, BlockYear, BlockQuarter, BlockMonth, BlockFortnight, BlockWeek, BlockDay, BlockHour, BlockMinute.

We will see what the community gravitates toward. And in either case the abbreviations can be:

Solar: BCentury, BEra, BYr, BQ

Lunar: BMo, BFort, BWk

Terrene: BDay, BHr, BMin

Here are the formulae for the longer intervals

BCentury = int(B/5,250,000)+1

BEra = int(B/210,000)+1

BYr = int(B/52,500)+1

Within a given year, the quarter and month number are given by:

BQ = 1 + int (B/13125) — 4 * (BYr — 1)

BMo = 1 + int (B/4375) — 12 * ( Byr — 1)

One good thing is that we have no leap years, although there are definitely parties at each 4 BlockYear intervals for Halving Day.

The BlockYear has 52 weeks plus an extra short day of 84 blocks (14 BlockHours). It also has exactly 12 BlockMonths. The BlockMonth has 30.382 days, or 30 days plus a short day of 55 blocks (9 BlockHours and 1 additional block).

Example: Block #596323 on 24 Sep 2019–09–23 07:53:57 UTC

Using the above formulae

BEra (596323) = 3, Byr (596323) = 12, BQ = 2, BMo = 5

and the block corresponds to the 10th fortnight, the 19th week, and 131st day of Byr 12.

A More Accurate Basis For Analysis

I suggest that it is much more natural, appropriate, and accurate to do price, market cap, hashrate, transaction value and other studies on a Bitcoin Calendar basis, in order to examine correlations and co-integrations of these quantities with a time-related variable.

The results can then be converted to regular Gregorian calendar time after the analysis for presentation purposes.

Have a nice Block Day!

Share this: