Month and Year for each new million BTC in circulation
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Please say the Month and Year when there were or there will be:

1 million bitcoins in circulation
2 million bitcoins in circulation
3 million bitcoins in circulation
4 million bitcoins in circulation
5 million bitcoins in circulation
6 million bitcoins in circulation
7 million bitcoins in circulation
8 million bitcoins in circulation
9 million bitcoins in circulation
10 million bitcoins in circulation
11 million bitcoins in circulation
12 million bitcoins in circulation
13 million bitcoins in circulation
14 million bitcoins in circulation
15 million bitcoins in circulation
16 million bitcoins in circulation
17 million bitcoins in circulation
18 million bitcoins in circulation
19 million bitcoins in circulation
20 million bitcoins in circulation
21 million bitcoins in circulation

There is a chat room on IRC freenode for: #bitcoin
You can read Satoshi whitepaper and do the calculations.
Easy task. Simple calculations. Past ones you can check if correspond to your calculations.

Tags
bitcoin

Crowdsource coding tasks.

3 Solutions

No. That's not the answer.
Ruth J 5 years ago
That's the most you will get from me for $1.
jb2 5 years ago
Winning solution

I actually did this as a technical exercise. $1 is extremely low but I'd post my solution, explanation and commented Java code for 20.

Assuming 600 seconds per block from the beginning turns out not to be very accurate when compared to what's actually happened (due to the fact that the network hashrate increases continuously while difficulty only adjusts every 2016 blocks, so on average blocks are mined slightly faster than they're supposed to be). I corrected for this by looking at the actual time it's taken for all blocks to be mined so far, and also for the last 50,000 blocks, which should give an accurate prediction.

It's worth noting that the Bitcoin circulation will approach, but never reach 21 million. The block reward will be zero after the 33rd halving, and we'll be left with 20,999,999.9769 BTC.

Forgot to add - my Bitcoin address is 13F7ZwefAyFXbNw2cnEKf1rWrw3P8xJJKv
Liam_ 5 years ago
The bounty is just for $1. If no valid solution is posted I will consider sending the $1 to a charity as this site gives me this option.
Ruth J 5 years ago

Commenting only allows me 800 characters, so here's the solution, bounty sent to the EFF.

Here are the timestamps for the millions that have been mined so far:

1000000: 2009-07-22 20:42:19
2000000: 2010-02-13 12:04:24
3000000: 2010-06-09 03:22:27
4000000: 2010-09-16 06:03:47
5000000: 2010-12-29 11:57:43
6000000: 2011-04-25 00:20:01
7000000: 2011-08-07 18:49:38
8000000: 2011-12-31 18:13:04
9000000: 2012-05-13 19:21:11
10000000: 2012-09-22 11:45:59
11000000: 2013-04-06 19:44:21
12000000: 2013-11-16 22:09:06
13000000: 2014-07-10 00:04:51

A simple calculation based on 600 seconds per block from when Satoshi started mining gives us the following:

1000000 BTC mined by: Thu May 28 01:14:25 BST 2009
2000000 BTC mined by: Tue Oct 13 22:34:25 BST 2009
3000000 BTC mined by: Mon Mar 01 18:54:25 GMT 2010
4000000 BTC mined by: Sun Jul 18 17:14:25 BST 2010
5000000 BTC mined by: Sat Dec 04 13:34:25 GMT 2010
6000000 BTC mined by: Fri Apr 22 11:54:25 BST 2011
7000000 BTC mined by: Thu Sep 08 09:14:25 BST 2011
8000000 BTC mined by: Wed Jan 25 05:34:25 GMT 2012
9000000 BTC mined by: Tue Jun 12 03:54:25 BST 2012
10000000 BTC mined by: Mon Oct 29 00:14:25 GMT 2012
11000000 BTC mined by: Sat May 25 09:14:25 BST 2013
12000000 BTC mined by: Thu Feb 27 02:54:25 GMT 2014
13000000 BTC mined by: Mon Dec 01 21:34:25 GMT 2014
14000000 BTC mined by: Sat Sep 05 17:14:25 BST 2015
15000000 BTC mined by: Thu Jun 09 11:54:25 BST 2016
16000000 BTC mined by: Mon May 22 17:14:25 BST 2017
17000000 BTC mined by: Thu Nov 29 05:34:25 GMT 2018
18000000 BTC mined by: Sat Jun 06 19:54:25 BST 2020
19000000 BTC mined by: Sat Nov 26 13:34:25 GMT 2022
20000000 BTC mined by: Mon Nov 23 21:34:25 GMT 2026

As you can see, this doesn't match what's actually happened because hashrate increases continuously while difficulty increases in jumps, i.e. as long as the moving lines are above the straight lines here, the average block time is less than 600 seconds.

Since the start of Bitcoin, the average block time has been 560 seconds, which gives us:

1000000 BTC mined by: Mon May 18 19:01:05 BST 2009
2000000 BTC mined by: Fri Sep 25 10:07:45 BST 2009
3000000 BTC mined by: Tue Feb 02 00:14:25 GMT 2010
4000000 BTC mined by: Fri Jun 11 16:21:05 BST 2010
5000000 BTC mined by: Tue Oct 19 07:27:45 BST 2010
6000000 BTC mined by: Fri Feb 25 21:34:25 GMT 2011
7000000 BTC mined by: Tue Jul 05 13:41:05 BST 2011
8000000 BTC mined by: Sat Nov 12 03:47:45 GMT 2011
9000000 BTC mined by: Tue Mar 20 18:54:25 GMT 2012
10000000 BTC mined by: Sat Jul 28 11:01:05 BST 2012
11000000 BTC mined by: Thu Feb 07 20:41:05 GMT 2013
12000000 BTC mined by: Fri Oct 25 03:54:25 BST 2013
13000000 BTC mined by: Fri Jul 11 10:07:45 BST 2014
14000000 BTC mined by: Fri Mar 27 15:21:05 GMT 2015
15000000 BTC mined by: Fri Dec 11 21:34:25 GMT 2015
16000000 BTC mined by: Sun Oct 30 23:21:05 GMT 2016
17000000 BTC mined by: Mon Apr 02 12:47:45 BST 2018
18000000 BTC mined by: Tue Sep 03 01:14:25 BST 2019
19000000 BTC mined by: Thu Dec 23 14:27:45 GMT 2021
20000000 BTC mined by: Sun Sep 14 18:07:45 BST 2025

This also isn't terribly accurate because the hashrate has been changing very differently over time (at the start, a few people turning CPU's on or off could have affected the hashrate, now it increases more smoothly). Looking at the last 50,000 blocks (which includes the last bubble, up until now) gives a decent prediction of how the hashrate might increase in the future. The average block time during this period was 507 seconds.

My best prediction for the future:

14000000 BTC mined by: Wed Mar 04 15:19:35 GMT 2015
15000000 BTC mined by: Sun Oct 25 08:39:35 GMT 2015
16000000 BTC mined by: Sat Aug 13 19:19:35 BST 2016
17000000 BTC mined by: Sun Nov 26 04:59:35 GMT 2017
18000000 BTC mined by: Sun Mar 10 15:39:35 GMT 2019
19000000 BTC mined by: Sun Apr 11 12:59:35 BST 2021
20000000 BTC mined by: Sun Aug 25 19:59:35 BST 2024

My final code:

    double blockReward = 25.0;
    double circulation = 13113950.0;

    // Unix timestamp for block 314588
    // Assuming there won't be overflow problems in 2038
    long timestamp = 1407513281;

    int million = 14000000;

    for (int i = 314558; i <= 21000000; i++) {

        // Half reward every 210,000 blocks
        if (((i % 210000) == 0) && i != 0) {
            blockReward = blockReward / 2;

            // According to Bitcoin wiki controlled supply page, anything
            // after 8 decimal digits is disregarded, the reward is never
            // rounded up
            blockReward = (long) (blockReward * 100000000);
            blockReward = blockReward / 100000000;
        }

        circulation = circulation + blockReward;

        // Block 264558 was mined at unix time 1382150024
        // 1407513281 - 1382150024 = 25363257
        // 25363257 / 600 = 42272 blocks actually should have been mined
        // 600 * (42272 / 50000) = ~507
        // Also adjusted starting timestamp, blockReward, circulation, i,
        // million (To start at block 314558)
        // Starting circulation = (210000 * 50) + (104558 * 25) = 13113950
        timestamp = timestamp + 507;

        // Check when each million is passed
        if (circulation >= million) {
            // Convert unix time back to date and print
            Date time = new java.util.Date((long) timestamp * 1000);
            System.out.println(million + " BTC mined by: " + time);
            million = million + 1000000;
        }
    }
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