Hacker News new | ask | show | jobs
by odbol_ 3288 days ago
You're calculating what it would cost to store a string representation of a date. Which is silly. You should always convert to a timestamp for storage. You can cram way more info into a single integer than you can with a base 10 string. And the bonus is you verify the date's correctness before storing.

Even a 32-bit int could hold 11 million years worth of dates. And if your software is used for longer than that, you can just change it to a 64-bit long and have software that will outlast the sun.
3 comments
varjag 3287 days ago
Silly or not, that's the reality of punch card based technology (BCDIC later extended to EBCDIC). Punch cards pre-date electronic computers, and making a relay tabulator set-up working with binary formats is impractical.

As computer hardware grew out of that, it maintained much of the legacy, down to hardware data paths and specialized processor instructions. It was more than a programming convention.

link
wpietri 3286 days ago
They were stored in BCD at the time:

https://en.wikipedia.org/wiki/Binary-coded_decimal

That was the right choice for the era. As mikeash points out, your approach takes more bits and more CPU cycles. But it also takes a computer to decode. Any programmer can look at a punch card, a hex dump, or even blinkenlights and read BCD. Decoding a 32-bit int for the date takes special code. Which you have to make sure to manually include in your program, the size of which you are already struggling to keep under machine limits.

We've come a long way.

link
mikeash 3287 days ago
Systems from this era were probably using BCD rather than base-10 strings. A BCD date would take up 24 bits.

Running a complicated date routine to convert to/from 32-bit timestamps would also have cost a huge amount. These machines had speeds measured in thousands of operations per second, and the division operations needed to do that sort of date work would take ages, relatively speaking. All on a machine that cost dozens of times the average yearly wage at the time, and accordingly needed to get as much work done as possible in order to earn its keep.

link