Jump to content
  • Advertisement
  • entries
  • comments
  • views

The Ultimate Date Class

Sign in to follow this  


Just saw John Munsch's entry on date classes, and I too am puzzled by why date and time classes are inevitably so unworkable. For my own edification, I now present my own date class that's simple, elegant, and probably completely unusable.

First off, let's dispense with making "date" and "time" two separate things. A date is just a way to express longer times, so there's no need for it. Let's just call it "time". After all, the year 1532 is a "time", but 8:00 this morning is not a "date", so "time" is the better descriptor.

Now let's think of a data structure. An unsigned 64-bit integer is capable of holding millionths of a second for about 585,000 years, so let's go with that. That'll satisfy the game-geeks who need millisecond timing along with the epoch counters who want to know what day of the week was July 4, 1776. We can even extend the calendar back a few thousand years. Let's make our pivot-point the date of the moon-landing (certainly a significant date, and much closer and easier to pinpoint than any ancient religious events), so our date object will be able to cover millionths of a second from approx 290,502 BCE to 294,440 CE. So you'll be able to use this time-object to track the journey of early protohumans across the Siberian landbridge, but you won't be able to track the progress of the Eloi and the Morlocks. Still, it's a good range and resolution.

. . .and Eloi and Morlocks weren't real anyway.

I mentioned before that this Ultimate Time Class of the Universe is probably entirely unworkable, and now's where it gets hairy. While it's got excellent resolution and range and not-unreasonable size (8 bytes ain't bad for computers today), the math necessary to calculate anything would be frighteningly ugly. To convert a 64-bit integer of microseconds into a "Tuesday February 24, 2004, 3:51 PM CST" would require some seriously ugly math, especially taking into account the little games that mankind's been playing with time ever since. . .well. . .time began. Things like adding or subtracting "leap seconds" now and then, and the Gregorian Calendar Reformations (when Pope Gregory III in 1582 declared that the day after October 4 would be October 15 to get the calendar back in sync with astronomy).

Maybe it won't be too ugly. Here's the code from my original date class that converts a month, day, and year into a Julian date (number of days since Jan 1, 5713 BCE). You'd think it'd be pretty hairy too, but it's not bad.

void Date::DMY(const ui8 &rDay, const ui8 &rMonth, const ui16 &rYear)
ui8 MonthToUse(rMonth);
ui16 YearToUse(rYear);

if (MonthToUse <= 2)



MonthToUse += 12;


i16 a = YearToUse/100;

nDate = (ui16)((i32)(365.25*YearToUse) + (i32)(30.6001*(MonthToUse+1)) + rDay + 1720994L + (2 - a + a/4));


Oh, and for those who don't care about any of this, July 4, 1776 was a Thursday. Now you know something new.
Sign in to follow this  


Recommended Comments

There are no comments to display.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Advertisement

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!